Don't try to be what you aren't. Find out who you really are, and be the best you can possibly be.
As you grow up you will admire people who have a certain way about them. Something that you find very appealing. People who are popular, celebrities in the music or film industry, models, or even athletes. You might want to be just like them. So you begin to emulate them, by dressing like they do, acting like they do, and even talking like them. The only problem is that you are not them. You are you. Take the time to find out who you are, not who others are. The people that are self-confident are those that are being their best selves. Find out who you are and be the best you possible.