Believe it or not, for eternity we are bound by our promises. Until we redeem them,we will always be in debt. It is immaterial whether the promisee let you off the hook, or discharged you of the responsibility to fulfil the promise. After all is said and done, you HAVE to fulfil your promise.
People should learn to not make promises they cannot keep. Promisees should in turn not limit the abilities of the promisor to keep his promise.
So personally, I am wary of promises, no matter how little they are, or how easy they would be to keep. And the few I make, I make out of genuine love and/or concern. Those promises, I INTEND to keep. Sooner or later, I will keep them. Because, even if I'm not on good terms with whoever I promised stuff, if I loved them enough to actually make that promise, then I will always feel obligated to fulfil them.
And believe it or not, every human is like that. Or supposed to be. Except, of course, you lied.