Stop believing in yourself and stop telling others to believe in themselves, too. Self confidence is a trailing indicator that occurs after you get some successes under your belt. Imploring others to have that confidence early does them no good and makes you sound like an inspirational poster.
Instead of believing in yourself, have a recipe for change. Simple and foolproof, when followed to the letter it makes 1 dozen awesome every time. Adjust cooking time for altitude and human. Follow that recipe a few times and self confidence will follow.
You've got to find that recipe for yourself, though. Here are some places to start looking: