Always be a person of your word. If you say you will do something, then do it. I had a friend who would say she would meet me for lunch and then shortly before we were supposed to meet, she would cancel. Sometimes, the call came minutes before the appointed time. There were times when she would agree to come over my house for dinner and then the day before or the morning of, after the groceries had been purchased, she would cancel. My husband and I dealt with it for a long time but after many cancelled dates, we finally said enough.
I was brought up that if you can't keep an appointment or do something you know you won't have time to do, then don't say you will. It's so much worse to cancel after the other person is counting on you. Have the courage to say, "I won't be able to attend," or "I can't head the committee this year." Cowards say they will because they cannot say "no" to someone in person; they would rather renege by phone or email. How sad.