The fear of being "not good enough" is one of the deepest fundamental fears we as human beings have, and these negative thoughts can sabotage our self esteem and success. The first important thing you need to realize is that the whole ""I'm not good enough thing"" is not personal to YOU. Everyone goes through it. You also need to understand that these negative thoughts don't go away over time and you have to work at conquering them consistently to stay on top of your game. In addition to understanding the key points above, you'll learn one specific juicy phrase you can say to yourself to get back in gear when the fear that you're not good enough is getting you down.
https://www.marieforleo.com/2012/03/feeling-not-good-enough/ Training yourself to come back to the moment and re-engage in the task at hand is the secret to breaking the self-doubt pattern once and for all.