To make a promise is to take upon yourself a responsibility. If you promise someone you'll give them or do something, you're basically telling them they can surely expect you to deliver on it. I feel most of us have made a promise we couldn't keep at least once in our lives, and at least once, we've also been on the receiving end.
A broken promise doesn't necessarily stem from dishonesty; sometimes we make promises we genuinely don't realize we can't or won't be able to keep.
If I had to narrow down the reasons we make promises, I would easily decide on two: to please, or to gain.
Promises to Please
Promises made to please people often stem from the genuine desire to make someone happy with the idea of receiving something.
Such promises exist to allow them to look forward to it, but the larger the expectation, the more responsibility rests on the one making the promise to deliver.
Truth be told, you don't need to make a promise just to tell someone you want to give them something.
Promises to Gain
Promises made to gain are done in expectation of things likewise material or not.
Simple examples include promising to do something in return for an amount of money, object, or favor one needs soon, or promising someone you'll do better to gain their trust or forgiveness.
Such promises have a greater weight to them, as you are receiving something in return for it. While the other kind of promise only risks disappointing the receiver of the promise, this one implies your own acknowledgement of something owed to someone.
On Expectations
As a promise maker, it's your responsibility to do your best to keep the promises you make.
If you're not sure you can do or give something, skip the promise altogether. While telling someone you want to do something for them still gets their hopes up, making a promise implies certainty, so try not to get overconfident.
As a receiver, you shouldn't bank too much on someone's promises, let alone set them as the sole foundation of your plans and actions.
Words are powerful, yet often fickle. Expect the best, but still prepare for the worst. Unforeseen and uncontrollable circumstances may still cause broken promises, so there are times you can't hold it against the promise maker.
True Promises
I've never been one for making promises, at least those beyond reassuring someone of things I certainly feel or believe. Promises, in my opinion, are a matter of not only one's ability to fulfill them but also one's determination to make sure they fulfull them, regardless of changing circumstances.
To me, the truest, most honest kind of promise is one made with every intention to see it through. Confidence alone does not make for a strong promise; without the genuine desire to do everything in one's power to prove its reality, a promise is as good as one not made.