Do not be discouraged by anything. You are in control of you and what you do. You have the power. Do not fall into the the trap of a negative state and if you do have ways to get yourself out of it.
Your body and mind are connected as one. Make sure your body language and posture are confident. This links to the brain and will increase your confident state.
If you are not feeling great then fake a smile. Faking a smile can have the same side effects as the real thing. The way you feel is changeable. Work backward and remember a time you felt great. Where were you? Who were you with? What were you doing? Enhance this memory and gain that feeling all over again. Just remembering this moment will bring back that feeling. Learn to master this recall and you will be able to control how you feel.