Figure out what you are meant to contribute to the world and make sure you contribute it. If this requires public speaking or networking or other activities that make you uncomfortable, do them anyway. But accept that they're difficult, get the training you need to make them easier, and reward yourself when you're done.

Quiet: The Power of Introverts in a World That Can't Stop Talking (ed. Penguin UK, 2012) - ISBN: 9780141970172