Disengaged

"And I could look into the crowded morgue of mistakes. The sun stopped its smile and frowned on me, too."

In the past, he would lament his mistakes. But he realises now that thinking about his mistakes as mistakes is a mistake. His "mistakes" were actually beneficial to his current transformation all along.

"My re-built/re-mastered heart is smashed into its faces, and its face is confused."

As he changes, he feels better and more confident about who he's becoming; just as he was confident before his confusion.

"I cut my throat in two. I said 'sorry' to you for being a fool, but I didn’t forgiveness; it was regret--not an apology--it was regret."

For the mistakes he percieved, he would appologise but he wasn't sorry he only regretted it. But now that he doesn't see the past as a mistake, he only has the future to look to and to become what he knows he can become.

"Disengaged, you’re with me, against me but the only thing forever is hate."

Everything he did to try to change in the past made people "anything with a dis- in it" and he realises that there's always going to be someone who's dissatisfied with him and accepts that because he's confident in who he's becoming.

"I forget what I saw before and after that day. I’d trade all I was worth to make myself in to the handsomest gun, and put the diamond bullet into your 404 ERROR face."

Here he talks about "when someone threatens what I love or care about." And to defend that, he has to be "a person no one wants to fuck with."

"And I’m an event everybody knows. You decide if you can live or you decide to let someone decide for you."

Here he talks about how he was, and tells people that they have the same choice he once did. And that's what the second sentence in the line is.

"And I could look into the crowded morgue of mistakes. The sun stopped its smile and frowned on me, too."

When he looked back into the past, it did nothing but make him miserable.

"My re-built/re-mastered heart is smashed into its faces, and its face is confused."

As he changed from the way he was, he discovered new things about himself and even still in the present discovering himself

"I cut my throat in two. I said 'sorry' to you for being a fool, but I didn’t forgiveness; it was regret--not an apology--it was regret."

He talks about the distant past

Disengaged, you’re with me, against me but the only thing forever is hate."

He has let go of the past, but he knows now what that relationship was about the whole time.

"I forget what I saw before and after that day. I’d trade all I was worth to make myself in to the handsomest gun, and put the diamond bullet into your 404 ERROR face."

All he can remember is one day with her, and he can't really even remember what she looked like; all he knows is that he was in love with her and he may have done it differently

"And I’m an event everybody knows. You decide if you can live or you decide to let someone decide for you."

Everyone knows what he'd have done, and it was up to her to decide then.

404 ERROR face!!!! loved it !!! haha that error in internet for those who don't know mean that the page does not longer exists...maybe everyone knows that and i'm just an idiot :)