Ditto on the martyrdom-- what GEL said. To stay with someone because you feel you owe them something when you don't love them and don't want to be there-- this is NOT doing them any favor! By all means, set this person free to find someone who really does love them! You think you're the best s/he will ever do? What makes any one of us such a prize that we inflict ourselves year after year on someone we don't want to be with? That's not guilt, that's some variety of arrogance.
Maybe s/he's sticking around because he thinks s/he's doing YOU a favor. Why not do each other a favor and move on? (Remarks not addressed solely to Chrissy.)