If you have trouble keeping your promises, don't make them! You are free not to say anything when you have nothing to say! Stop making void promises! If you like the sound of your own voice so much that you cannot keep quiet, sing a song or read a book out loud. You don't have to make promises to people if you are not loyal to your words. It is so easy to keep quiet when you have nothing to say. Every promise that you cannot keep slowly ruins your integrity.
I believe in you!