Confidence breeds success. As you accomplish the things you set out to achieve, your confidence in your abilities will grow. You can experience this increasing confidence by trial and error. Or, you can shorten the learning curve dramatically through a mentor.
Find the person who's the best at what you're trying to accomplish. Approach that person and ask them to show you the ropes. Ask them to show you how they arrived at their success and how they maintain it. With a mentor, your chances of success increase dramatically, thereby strengthening your confidence.