When you make a commitment, stick to it no matter what. Your ability to do this will not only build your character but your belief in yourself as well.
I once read an analogy that compared commitment to throwing rocks into a river. If you were to commit to throwing 1 rock a day into a river, then that is what you must do each day, no matter what. Although you can simply skip a day and throw 2 rocks the next day to make it up, you must not do that. It would certainly be easier to skip several weeks and just throw a handful of rocks into the river to make up for it but that would mean you are breaking your commitment.
If you actually commit to doing something, then you must follow through. That way, whenever you tell yourself you will do something, you will have the confidence that you’ll actually do it since you always do what you say you will do. What you say and what you do will be congruent.
The bottom line is to get yourself to do what you were committed to doing no matter what. It won’t always be easy but it’s what will separate you from the average person. If you find yourself constantly failing to follow through, make smaller commitments and build up from there.