I recently resolved to, at the start of each day (I look myself in the mirror while brushing my teeth) tell myself "I resolve to find one opportunity today to give my guy a little love at the moment I don't want to."
I sometimes know my guy is trying to make me laugh, lighten the moment, indirectly ask for my forgiveness, obliquely show that's feeling overwhelmed, etc, etc, and because of the anger, sadness, loneliness, you name it, that I perpetually carry around, I turn away and miss the opportunity for a little closeness. I struggle mightily with "He doesn't deserve it. What about me? When he does better, then I'll do better." Ugh.
This resolution / commitment I make to myself has had two effects. It creates a little tiny moment of delight that I am still capable of compassion for my life-long mate, or I sometimes see a little ease come over my guy's face, just for a moment. Second, and most difficult, I am ashamed of how often in a single day I find the opportunity to exercise my commitment. You don't see what you don't look for.