How can improve my self-esteem as a disabled person?

Be Productive. Find something you can do through volunteerism; start a home based business. Anytime you are helping others adn making an income you will have good self-esteem. I have seen a couple of people that were born with no legs and no arms that became motivational speakers and learned to do many things for themselves.
Acknowledge yourself. In general focus on your talents and abilities than your difficulties. Avoid "should"ing. If you fail at something try to remind yourself that you "made a mistake" and that you are "not the mistake." be realistic in your goals for yourself.