No matter how small. Don't make any you can't keep. Be honest, forthright, straightforward. Don't mislead or tease or hint that you will do something when you know you will likely do the opposite.
I am so sick and tired of people flaking out, forgetting what they said, making promises or appointments they knew they couldn't or didn't want to keep and elevating others' hopes in bad faith. Stop with the bait-and-switch, the disappearing act, the just-couldn't-handle-it mentality.
If you do this, you will slowly make people hate you. You will also slowly succumb to a lifetime of bad faith actions, which puts you on a path to ill-will, bad karma and endless victimhood.
Don't do it. No excuses. Just don't.
Be responsible, keep your commitments, and don't make any you can't keep. Whatever it is, act in good faith.