How can you acquire and maintain frame? What is your strategy?

Simply repeating the mantra "I am Chad Thundercock" all day does not seem to be effective. Doubts start to arise, leading to rationalizations and excessive humility. Deep down, I know that I am genuinely proficient, better than 90% of men. However, one small error can shake my confidence. I want to improve but I also start to rationalize, causing my confidence to crumble.

How can I prevent this from happening and truly believe in what I tell myself?