I don't know what it is but some days are just worse than others. Wife and I don't talk, really only for when words needs to be exchanged. Had roommates in college who I hated but we'd still talk occassionally. Sex? Hadn't happened in years and no chance of it: I stay because it made sense with kids but I am close to seeing youngest graduate and there being no reason to be here. Take the house, spousal support, 50% of the retirement and go live your life. BUT I still stupidly hope that something changes one day.

ETA: I've thought about taking a job overseas and just living separately for several years. Anyone do this?