One common trait of highly confident people is that they are exposed to different experiences. The more exposure someone has, the more knowledge and wisdom he acquires in his life. This is true for exposure to people or experiences. I remember when I was younger, I did sports and traveling so that I can improve my confidence. It is because there was a time when I could not travel or afford to travel and so I worked hard to increase my exposure, be it eating at a fine dining restaurant , or traveling alone to a new country. Those experiences helped me develop myself.