One thing that helps me is to consciously decide to accept it. Like, I realize that I have the choice to react in several different ways. I could argue, I could walk away and do nothing, I could go the thing by myself even though everyone else canceled, or I could go with them and do something else.
Making a conscious decision about it takes it from "something that was done to me" and makes it into "something I I have a choice about".
This is going to sound like the dumbest thing ever, but here's how I learned that:
I usually have the exact same thing for breakfast every morning (oatmeal and a boiled egg - very simple, not fancy at all). One morning when my wife's parents were visiting, I got up and they were already downstairs cooking. My mother-in-law happily announced that she had made me breakfast. As good as it looked, I didn't want that fancy breakfast - I wanted my plain old routine breakfast. Rather that blow up or insult them by refusing the food, I realized I could make a conscious choice to choose to have something else for breakfast. I chose to eat what they made, and because it was my choice, I was able to deal with the change.
I'm sure that most people would think that was the most trivial and meaningless change, but it upset my routine. Since then, I've been able to "consciously choose" to accept other changes, some big and some small.