Every canceled plan is a small withdrawal from your trust account. Watch the balance.

One cancellation is nothing and a pattern of them is a message. Each time, the other person quietly adjusts their estimate of whether you will actually be there, and eventually they stop making plans with you rather than risk the disappointment. The account is real even though nobody mentions it.

Picture yourself at that hour on that day before you agree, and answer honestly. Say no earlier and more often, so the yes holds. If you do have to cancel, do it as far ahead as you can and offer the replacement date yourself.