How to boost one's self-confidence?

One can be repeat in a loud voice in front of a mirror : I can do it, I can do it, I can do it, I can do it, I can do it, I can do it.

That is a good self-motivation. 

Doesn't sound like much but always tell yourself that you are better than every person on the Earth in at least one area. Look at that person in your life who's gotten good grades, a good job, and a good life. Well guess what? That person would beg for something of yours. Whether it be the love of your spouse or the happiness you share with your friends he's on his knees asking for it. It sounds awful but it gets me through the day, well maybe I'm just a sadistic person.