Remember that embarrassing thing you did?
Nobody else does.
Self confidence boils down to not worrying about what other people think about you.
In psychology there is the research to prove that people think they are noticed much more than they really are. This is termed the “Spotlight Effect”. But the reality is you aren’t in a spotlight, other people are not looking at you, they have their own problems and are worrying about what you and others think about them.
If you don ‘t immediately agree with me ask yourself this question. How much time do you spend thinking about other people when they aren’t standing in front of you? Very little, I bet.
So fake it till you make it as the american saying goes. Other people will take what you say and do at face value.
So act as if you are full of self confidence, other people will assume that is who you are.
And sooner or later you will no longer have to act, it will become part of your personality.