Well, it is a very similar process. When your mom postpones meeting up and you feel bad, it’s like a trigger. You can ask yourself, “how do I feel about my mom not meeting up with me?” and allow yourself to feel whatever emotions come up. Keep asking yourself the question and keep allowing yourself to feel. You could also ask, “When was the first time I felt this way?” An image may pop up but feelings definitely will, and then you feel from that.
Another thing is to journal. This works better for some people. You can externalize your emotion and chip away at the emotional entanglement, as long as you’re honest about how you feel.
Maybe I should write something longer about this because I know the feeling, but I hope this helps.