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I have noticed a pattern in myself, which I suspect could be true for others too. Namely, that I am much more likely to care about someone if the feeling is mutual. On a rational level, I can recognize that this or that person has had a bad time and deserve better, and I want to help them, but if they are hostile or indifferent to me, I kind of stop caring. And vice versa, if I feel that someone cares about me, I will care a lot about them. If this is the case for two people, it can quickly spiral either towards more mutual caring, or more mutual indifference.
Now here's the tricky part, how do we influence this trajectory? The only way I can think of is to care even if the other person isn't caring back. Polarizing language can feel good, to assert yourself when you feel hurt, but... is it helpful or detrimental for the bigger picture? It's so circular and self-reinforcing. So hard to escape.
I get the feeling that many people argue that "well, when they start treating me right, then I will start treating them right, but until then I don't care", and sure, I understand that feeling. But the feeling is probably mutual.