A couple of days ago, I wrote about working with difficult people. Simply don't work with them. There are too many other people who are willing to work with you to bother with the difficult ones. I'm in the middle of negotiations and frankly will have to decline. Not over price, not over what the property is. It's over who I will work with. Forgetaboutit. Not worth it. Sometimes you have to learn to say no.
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.