We promise we will be better, that we will do this or that, that we will change. Those who hope in those promises are often disappointed because the one making the promises is usually the one who has left so much undone that promises of doing better are needed. Red Auerbach wrote, "An acre of performance is worth the whole world of promise."
We rejoice when we meet a person of their word. There is a quality of character in such a person that we admire. Jesus Christ was a little more forceful in His comment. He said, "Let your 'yes' be ‘yes' and your 'no' be ‘no' for whatever is more than these is from the devil" (Matthew 5:37). Promises are usually a "yes" that has not been carried out. When we make a promise or the more official vow—just do it! That is what God would have you do.