I used to have a problem saying no and then I would commit to something and cancel at the last minute and made lots of people mad at me.  I knew I could work on my commitment issues, and do things I promised to do even though I didn’t want to, and while I resented having to face the consequence of my actions.  Or I could just stop committing.  Work on that issue in another lifetime.  Let people get mad at me for being noncommittal rather than for disappointing them.