The practice of psychology

Inertia
She works in physics, and works in psychology. If you stopped and become dejected, then of course you should not expect any certainty. Start doing what works well for you, mark the results and move on.

Even the solution of the smallest problem lights a spark inside a person that can kindle a whole flame. Confidence depends on the actions. More action means more confidence, because the brain perceives actions as competence. The main thing is to start, and then we'll see. The solution starts an action, which then means confidence.

The theory, of course, you need to know, but practice helps to understand many things much more quickly. Nothing prevents you from absorbing the theory during practice and thus learning in the process of action.

Social life
Above we talked about the fact that you do not need people to be self-confident. This is true, however, when you are in a society, you can test your confidence in practice. How do you know that you are confident if you are sitting at home in front of a computer? It's people that are the criterion of your confidence.