I think you’re taking it too literally. When people say “fake it till you make it” what they mean is inculcate in yourself the attitude of the person you want to be rather than constantly thinking that you can’t be that person. For example, if you want to improve your health, think like a healthy person. If you want to work hard, start thinking like a person who works hard. Then automatically you begin to follow their habits and this ultimately leads you to becoming what you want to become. It’s reverse engineering. This is why, controlling how you breathe can often calm you down in moments of stress.
Although I can understand that sometimes “fake it till you make it” can be taken too literally even from the negative perspective. But in its true spirit, this advice is not bad.