Sometimes, for me, it depends on what the commitment is? I use to agree to go to friend's parties then call and cancel at the last minute. I'd feel bad but now, looking back on it 25-30 years later, it's okay because it was just a party. Sure I didn't do what I said I would but my self and health is more important than a "social" commitment.

Learn to word things when you agree to them, in a way you can wiggle out :-) Say something like, "I'll do it if I am able at the time" or, "I'd like to but I'm not 100% sure if I will be able to." Let the other people know you have "health" problems and might not be able to do whatever it is.

If it is something for another person whom I love, I bite the bullet and do it anyway. If it's something over time, I will try to understand how I "work" best and see if I can't do it a little bit at a time, here and here or I'll just do a one-time push at the end, depending on how I work on that sort of commitment. Knowing and trusting myself and knowing that we usually manage to do/afford what we really want, I remind myself why I agreed to do whatever (good to think about it before commitment and make sure you really want to do it and aren't just committing because you feel you should or for "guilt" reasons).

Another good thing I've used to get moving in the past is to look beyond whatever it is that I have to do and look forward to something afterwards. When I had to terminate with my T, I set up "bridge" things along the way that I was interested in that had nothing to do with her and also had a trip planned (and was moving to a new house :-) the month or two afterwards. I was plenty busy so there was action happening in my life that wasn't about T and terminating. Think up some "reward" for after you do whatever the commitment is and focus on that and the commitment often won't feel as difficult.