to me, this can apply to an ending of a relationship for other reasons than death. he was stubborn and would not forgive her, which he now regrets. he thinks about her, wonders if she is thinking of him. ("i wonder aloud, if you're watching over me") saying he will unlock his "door" is saying that he will admit his true feelings. "passing the Cemetery Gates" is saying he will come to terms with what happened, and go on with his life.
to me, this can apply to an ending of a relationship for other reasons than death. he was stubborn and would not forgive her, which he now regrets. he thinks about her, wonders if she is thinking of him. ("i wonder aloud, if you're watching over me") saying he will unlock his "door" is saying that he will admit his true feelings. "passing the Cemetery Gates" is saying he will come to terms with what happened, and go on with his life.
but that's just what it meant to me.