Taking Back Sunday - What's It Feel Like to Be a Ghost? Lyrics Meaning

The song is about a dysfunctional relationship. "And then you said a little more about your dreams, like that was my call" is suggesting that his partner was dependent on him to make her existence, and she relayed her dreams to him with the intention that he would use the knowledge to help her. "Bypassed everything and went straight for the neck" could be insinuating that finally he is forgetting all the drama and discussing the issue at hand immediately without trying to dodge the issue. "What's it feel like to be a ghost?" does not mean an actual ghost but could be referring to the ghost of her former self, a mere shadow of a person. "Are you up or are you up for this?" could be his way of saying the issue is at hand, a cure is to be obtained, but is she up for facing reality and conquering her ghost-like state? "This is quick but not quite painless, it sits perched on your arm." may suggest that the arguments they have are always quick and filled with pain, or she tends to act out with a quick and painful addiction that taints her -self mutilation (perched on your arm -tacky and irrelevant: she cuts herself which is tacky and in his opinion unnecessary). Simply put, the song is about a dysfunctional relationship with a girl who is too codependent on him for the relationship to flourish.
Tacky and irrelevant. (So what?)
A permanent reminder that oh christ.