Remember, you don’t always have to feel a particular way to act in a particular way. Every time you step outside your comfort zone, it grows a bit until one day when you do the action that’s currently causing you concern, you realise it's now actually within your comfort zone!
Your habit has been to feel and think in a certain way and now you're training yourself to feel and think in a different way. It takes time and consistent action.
When you move and act differently, you can affect how you feel. This means you can take control of your actions, and your thoughts and feelings will be affected. Act confidently, and think confident thoughts, and eventually you will feel confident as well.
“If you always do what you’ve always done, you’ll always get what you’ve always got” - Henry Ford