Here's a piece of advice that has worked on some people, that uses a principle you should get very familiar with as an SS.
Sit calmly, by yourself, with a paper in front of you, and write this question:
"Do I like myself?"
Simply look at yourself objectively, as you would when asking yourself if you like someone else.
Write any thoughts and courses of thought that come to mind. What do you like about yourself? What do you dislike? Why? How can you change it? If you can't change it, how can you work around it? How can you accept it?
Many, many more questions will come.
Sit with that question and don't get distracted for maybe 30 minutes to an hour.
Do that more than once if you need to.
Self-confidence is a state that is earned with time, as your perceived image of yourself is something that is part of your "thought habits", and thought habits, thought patterns, take time to change, as this is "changing yourself".
This is important as an SS, as you should know your mind, know how it works, and know how to get it to work in your favor. It's a key element of magic that I don't see emphasized by members here enough.