When it comes to things you can control, which are your own actions, you need to be completely cautious. If you do so, you can succeed in your aim. When it comes to things outside of your control, which are the actions of others, there you can be confident, because those actions don't belong to you anyway. Yet some people have this backwards. They worry more about the things they can't control than the things they can. This is a waste of precious time and energy.
Keeping promises is hard. It requires us to do things we don't want to do. But keep those promises you must do. Otherwise, do not make them in the first place. But since you have made them, you must keep them, especially if it would benefit all those involved including yourself.