One of the easiest ways to become more confident is to praise yourself more often. Self-praise builds your self-confidence and ability to manage any task.
There are a lot of ways to do this positive mental practice.
For example: every morning, start each day with positive self-reinforcement. As soon as you wake up, tell yourself, today is going to be a fantastic day. I am an important person who matters. I will be able to handle all the problems that come my way. Nothing can bring me down. Keep repeating this to yourself. And very soon you will feel a great surge of energy kick in that will carry you forward.