Lyric discussion by SeanMurphh 

Cover art for Sad Savior lyrics by Taking Back Sunday

I think this song is about a relationship, and possibly having to come to terms with certain things your partner has done in the past, and deciding whether or not you can accept them and move on.

"That brutal youth exhumed and removed entombed in a box cached across your room it slows our momentum each time I'm reminded it's there"

I think that means, things the person did in their past are sometimes brought up and thought about, and it slows the momentum of the relationship when you have to think about them (ie. the person being with another, an ex, maybe they have a history of cheating, etc.)