The kind person gives generously from a sense that they too will stand in need of kindness. Not right now, not over this, but in some other area. They know that self-righteousness is merely the result of a faulty memory: an inability to hold in mind, at moments when they are truly good and totally in the right, how often they have been deeply and definitively in the wrong.
One fundamental path to remaining kind around people is the power to hold on, even in very challenging situations, to a distinction between what someone does, and what they meant to do.
The modern world is very uncomfortable around the idea of a good person not succeeding. We would rather say that they weren’t good than embrace a far more disturbing and less well-publicised thought: that the world is very unfair. Kind people always keep the notion of injustice in mind.