Promises have the power to transform whoever gives them; but when, and only when, such promises are kept.
It is said that it is easier to keep promises given to yourself. Even Stephen Covey says that this is the way how to learn to keep them.
I disagree with that. If you promise something to yourself, it is very easy to break. Because nobody will know, but you. So your image in the eyes of others will not be shaken. Later you can calm down your conscience, finding dozens of excuses. All of them silly by definition, though.
So, having said all that, the easiest way to get transformed to something better is to give promises to yourself and keep them. Always.