Fake it till you become it

Act as an self confident person till you eventually become one. Our bodies govern how we feel about ourselves; just like animals, people tend to shrink when they have slim self confidence, and expand when they have high self confidence. These postures are called low power poses and high power poses. You must implement high power poses in your life.

I suggest this great Ted talk if you want to learn about it more, and here are the examples of high and low power poses: https://www.youtube.com/watch?v=Ks-_Mh1QhMc