I find that my self-confidence is boosted by doing the right thing even if it's difficult. We all have choices that we can make that will make us feel better or worse about ourselves. I agree that the choice of attire makes a big difference. Once upon a time I read and have been told "dress for the job you want not for the job that you have."
When you perform your personal and business life actions and speak with integrity you build a reputation and boost your self-confidence.
Just because I look in the mirror and say I am a wonderful person does not make that true. The actions that I perform day-in-and-day-out will make me feel better about who I am and will increase my reputation score in the community.
Right now it's an invisible score, but I have read that in China there is such a thing as a social media reputation score somewhere.
There was a movie that I watched once where you were able to go online and boost or lower the score of another person in your community circle or school. As horrific as that is, we all have a mental reputation score surrounding the people and businesses that we associate with daily Have a blessed day.