Heartbreaking indeed :(

One thing I'm trying to practice and that is supposed to spare me the heartaches is learning to look at the other person's system of values. Once I realize what's important to one person, it becomes clear to me that they do x or y because they believe in z or w and none of the x, y, z or w has to do with me. I still get upset, but I can usually calm down telling myself - they do this because of that, that's what they believe in. It brings me back to what I believe in and how I can act according to my personal system of values.