So how long does one hold out in hopes things change? If you're in a marriage, been married for a good while and things aren't working, how long do you stay? If you are the only one working on the marriage? if they seem to give you the illusion they are working on things to throw out bits and pieces or crumbs of making you think they made improvement, enough for you? Only for them to go back to the way they were until a month or two later when they decide to give you false hope again?
Kids are gone off to college or married. Or lets say you have no kids, so the kid excuse is gone. Staying for history together doesn't mean squat either especially if most of it has been you beating your head against the wall, trying to work it out when they haven't put forth much effort. Or even if they have and its just not there anymore.
Yes, I have also known people who have tried it all. Done this and that, said this and that, changed whatever. Went to therapy, blah blah blah, and still stay to beat a dead horse!
Maybe they like beating the dead horse? Maybe being miserable and constantly working on a marriage by themselves isn't so bad?