Sharing the position of the narrator, I'll try my hand at interpreting as well.
"So here goes" starting off is very much a phrase used to indicate reluctance in completing some action, a lack of confidence, motivation or desire to do the thing. In this case, I believe it's reluctance for lack of confidence and motivation--the narrator has the desire but "one last letter now, one last attempt to make sense" indicates he's losing hope in his ability to write to clarify his existential angst for himself or for others.
"What have I been trying to accomplish?" is not a literal misunderstanding of his action, but the emotional and mental fatigue from the intense existential thought clouding his mind as he's wandered through a labyrinth of uncertainty and profound doubt. The attempt to uncover the meaning and represent it makes things "blurry"--very comparable to the painting in Virginia Woolf's "To the Lighthouse", where the character Lily Briscoe attempts to find and represent truth and totality through art, a meaning, a reason, an essence, but paints a blurred picture. Life's many intricacies and tragedies are incomprehensible in finding a comforting reason, or a reason at all.
The narrator is having an identity crisis. He's adopted a skepticist mindset where he questions his very own self, because he's lost his own normal grounding in his self-defeating, self-examining behaviour. He recognises this shift and no longer knows if he is the same "voice" writing these stories, not as if he's changed as a person but rather that he is a stranger to his former self, his normal life, before the "departure". He doesn't even know if he's always been that way, that he's just uncovered his real self. It's schizophrenic and character, yet I honestly can't tell if it's metaphoric or it's simply a result of his existential depression.
"I don't know... I don't know." This is a melancholic, exhausted admission of defeat, not a cathartic acknowledgment of uncertainty.
"One last desperate plea..." means the letter and his last attempt to find clarity and hope it exorcises the demons, despite the fact that writing hasn't helped it at all ("A Poem"). He tragically sees it as a twisted comedy, as if his existential guilt amid normal lives is a situational comedy to others, as if it's something to mock. "Losing sanity" is pretty self-explanatory, and is an explicit recognition for the listener about what has been happening across the entire album. He asks if it's been "fashioned by the worst of me" and is not something that life has forced upon him, but something he's forced upon himself--he struggles with this question several times throughout the four monologues/letters.
The broken jar is symbolic of his life, his direction, his mindset and purpose, and the image of a shattered household item is also a symbol for a childish accident, which is reinforced by trying to reassemble the jar and being frustrated by the outcome--the cracks still show, no matter what. The entire album reflects a self-inflicted pain, an accident; I share the sentiment, and believe that, like me, the existential depression may not have been something entirely forced by a situation. It may have started happening as he kept questioning in this way. A tragedy cannot force one to question, the individual must question it first. And even if there was an event that occurred that set this downward spiral in motion, there was still certainly an accidental nature to the intensity of his own thinking and doubting. Self-examination at times may be natural, but intense existential questioning from tragedy is not inherently common.
He's trying to let go of something and someone. It's very unclear who he means--maybe the lover in "You and I in Unison" or his former self, or maybe both. I myself am struggling to decide whether or not to let go of what I thought was my former self, because I'm not sure if that self is real or not. After years of being trapped within your own mind, who you once were becomes alien and a tragically blurry memory, maybe even just a story or a fabrication in this context.
He mentioned before he doesn't want to forget, find a substitute, and be happy. These truths, this uncertainty and existential pondering, are probably extremely true, and the narrator does not wish to comfort himself in a lie that these things don't have a significance. He can't find it or cope with the mystery, though. His entire life now revolves around repairing the jar and finding the answers and meaning, but it's been damaging him far more as things pile on. He is Walter Benjamin's Angel of History, looking back at the ruin in awe and unable to look forward. He has applied this historiography to life and his existence.
The final part solidifies this is a frustrated, tortured post-modern piece. He cannot reason the meaning out, cannot repair the broken jar. Whereas the post-modernist would say this inability to find a totality/absolute in the ruin is okay, the narrator throws the shards out in hopelessness and accepts aimlessly leading toward the curtain call, death. Much like in "White Noise" by Don Delillo, the narrator contemplates his own mortality and how to live life properly without reason. He surrenders to proceeding toward death anyway, not in a dignified way, but as a tragic actor (curtain call).
As for hope in this, there is little to none. The final two songs offer some hope, but much less than the epic "The Last Lost Continent" in the first album. He does, however, return to love being the cure--an intimacy in sharing fear and life with another person. Whoever he's loved has left in some way, I believe through death, but it's open to interpretation. Yet he resolves to sing this lover's name with his and never let the bond sever though she's faded from mortal existence and his life. It's not an overly hopeful resolution, but certainly not a suicide.
Sharing the position of the narrator, I'll try my hand at interpreting as well.
"So here goes" starting off is very much a phrase used to indicate reluctance in completing some action, a lack of confidence, motivation or desire to do the thing. In this case, I believe it's reluctance for lack of confidence and motivation--the narrator has the desire but "one last letter now, one last attempt to make sense" indicates he's losing hope in his ability to write to clarify his existential angst for himself or for others.
"What have I been trying to accomplish?" is not a literal misunderstanding of his action, but the emotional and mental fatigue from the intense existential thought clouding his mind as he's wandered through a labyrinth of uncertainty and profound doubt. The attempt to uncover the meaning and represent it makes things "blurry"--very comparable to the painting in Virginia Woolf's "To the Lighthouse", where the character Lily Briscoe attempts to find and represent truth and totality through art, a meaning, a reason, an essence, but paints a blurred picture. Life's many intricacies and tragedies are incomprehensible in finding a comforting reason, or a reason at all.
The narrator is having an identity crisis. He's adopted a skepticist mindset where he questions his very own self, because he's lost his own normal grounding in his self-defeating, self-examining behaviour. He recognises this shift and no longer knows if he is the same "voice" writing these stories, not as if he's changed as a person but rather that he is a stranger to his former self, his normal life, before the "departure". He doesn't even know if he's always been that way, that he's just uncovered his real self. It's schizophrenic and character, yet I honestly can't tell if it's metaphoric or it's simply a result of his existential depression.
"I don't know... I don't know." This is a melancholic, exhausted admission of defeat, not a cathartic acknowledgment of uncertainty.
"One last desperate plea..." means the letter and his last attempt to find clarity and hope it exorcises the demons, despite the fact that writing hasn't helped it at all ("A Poem"). He tragically sees it as a twisted comedy, as if his existential guilt amid normal lives is a situational comedy to others, as if it's something to mock. "Losing sanity" is pretty self-explanatory, and is an explicit recognition for the listener about what has been happening across the entire album. He asks if it's been "fashioned by the worst of me" and is not something that life has forced upon him, but something he's forced upon himself--he struggles with this question several times throughout the four monologues/letters.
The broken jar is symbolic of his life, his direction, his mindset and purpose, and the image of a shattered household item is also a symbol for a childish accident, which is reinforced by trying to reassemble the jar and being frustrated by the outcome--the cracks still show, no matter what. The entire album reflects a self-inflicted pain, an accident; I share the sentiment, and believe that, like me, the existential depression may not have been something entirely forced by a situation. It may have started happening as he kept questioning in this way. A tragedy cannot force one to question, the individual must question it first. And even if there was an event that occurred that set this downward spiral in motion, there was still certainly an accidental nature to the intensity of his own thinking and doubting. Self-examination at times may be natural, but intense existential questioning from tragedy is not inherently common.
He's trying to let go of something and someone. It's very unclear who he means--maybe the lover in "You and I in Unison" or his former self, or maybe both. I myself am struggling to decide whether or not to let go of what I thought was my former self, because I'm not sure if that self is real or not. After years of being trapped within your own mind, who you once were becomes alien and a tragically blurry memory, maybe even just a story or a fabrication in this context.
He mentioned before he doesn't want to forget, find a substitute, and be happy. These truths, this uncertainty and existential pondering, are probably extremely true, and the narrator does not wish to comfort himself in a lie that these things don't have a significance. He can't find it or cope with the mystery, though. His entire life now revolves around repairing the jar and finding the answers and meaning, but it's been damaging him far more as things pile on. He is Walter Benjamin's Angel of History, looking back at the ruin in awe and unable to look forward. He has applied this historiography to life and his existence.
The final part solidifies this is a frustrated, tortured post-modern piece. He cannot reason the meaning out, cannot repair the broken jar. Whereas the post-modernist would say this inability to find a totality/absolute in the ruin is okay, the narrator throws the shards out in hopelessness and accepts aimlessly leading toward the curtain call, death. Much like in "White Noise" by Don Delillo, the narrator contemplates his own mortality and how to live life properly without reason. He surrenders to proceeding toward death anyway, not in a dignified way, but as a tragic actor (curtain call).
As for hope in this, there is little to none. The final two songs offer some hope, but much less than the epic "The Last Lost Continent" in the first album. He does, however, return to love being the cure--an intimacy in sharing fear and life with another person. Whoever he's loved has left in some way, I believe through death, but it's open to interpretation. Yet he resolves to sing this lover's name with his and never let the bond sever though she's faded from mortal existence and his life. It's not an overly hopeful resolution, but certainly not a suicide.