Are you fundamentally flexible and feel relaxed about changing plan or not doing something you set yourself to do, or do you have a hard time accepting that you have not fulfilled a goal you've set out for yourself?
Personally, although I'm Judging, if I understand the reasons for changing plans, I'm happy. For example, if I want to go for a run, and yet I wake up and feel ill, I won't run. It might annoy me a bit at first, but I can take it. I'm good at creating contingency plans.