I just realized something weird about my feelings. Actually, I'm guessing this is true of a lot of people and I'm going to write about in the second person, but there's always a possibility I'm just a huge freak.
Basically, things look better when you are comparing them to something worse. This means that the worse someone is, the more their behavior can impress you.
For example, if your best friend usually criticizes you and insults everything you say, you will feel so special when he does tell you, "That was really smart." He will seem really nice, and you'll feel like what he said was really meaningful because you waited such a long time to hear it.
If your boyfriend always hits you when he's mad, it will seem amazing if he gets mad and doesn't hit you. It will seem like he's great for controlling himself, like he's really working hard to treat you well.
Actually neither of these people is nice! It doesn't have to be this extreme. But the point is you give more credit to people who deserve less credit. Meanwhile, if someone is consistently kind to you, you never get the high of being shocked by an ordinary display of kindness. Their kindness blends into itself and doesn't impress you as much as someone not hitting you 1% of the time.
I think I first got exposed to this idea in the form of a piece I read about being nostalgic for bad relationships. It was basically about how bad relationships have some really exciting and good moments when your partner stops being awful for a minute and you're so excited about it. Then you end up being nostalgic when you're in a relationship with a good person, because you don't get excited the same way. (If someone could find this piece, I'd love to link to it--I just couldn't find it.)
This is pretty obvious, I guess, but I was thrilled to notice myself having one of these reactions today because I could self-correct. Here's to prioritizing people who are actually good to you most of the time.