Here's my pep talk...listen closely: Focus on your achievements rather than your failures. If you don't you'll find yourself thinking about how you failed. You need to look at ALL the things you've done well. And there are many things!
Do not be too competitive or compare yourself with others. Be yourself and accept that life is not a race against others.
Your self confidence depends on you and your personal needs. Have faith in yourself. You were born unique. You are you, and nobody can ever take that away. You are one of a kind.
And for those that try to put you down, always think that they are jealous of you. Let their jealousy lead to their own self destruction.
Always smile, brush your teeth, and expand your chest.
Without you the world would be different. Smaller by one, and small if definitely worst than big.