If fear of disappointing other people is what is keeping you in this commitment that you want to be out of, then you need to consider becoming a little bit ruthless. I always recoiled from that, myself, but found that what I used to consider being "ruthless" is actually a necessary stance to take once in a while, if I'm going to "own" my own life.

We can never have enough foresight to make sure we never never ever make offers that we end up regretting. That's why humans have the ability to change their minds. We have to distinguish between what is a real hard contractual obligation that honor demand we meet and what is merely something that seemed like a better idea than it turned out to be. You're being too hard on yourself, hvert. An ill-advised offer to help out on a committee at a social club is not a moral obligation. You have an obligation to yourself to use your time in ways meaningful for you.