Believe in yourself.
When you believe in yourself and you have high expectations for yourself then you will rise to the challenge. If you expect yourself to be able to complete tasks and solve things then you will rise to the challenge. Incidently, if you have little faith in your abilities you will never exceed your own expectations.
I heard this quote somewhere a while ago and although I know not the author it still rings clear in my head:
“Obedience is the greatest obstacle to discovering who you are- obedience to others, obedience to your own beliefs about your limitations.”