So how do you become more confident? Get a head start by telling yourself that you're gaining more confidence now. It helps!
Various experts add: being in good health, regularly exercising and taking care of your body, frequently participating in activities that are fun and not just working all the time, having some close confident friends that you can trust, and being happy in your single or married status.
Frankly, money gives you confidence too, from the sense of security it provides. Still, I know plenty of wealthy people who run scared.
The National Association of Realtors will tell you that owning a home increases self-confidence. (Oh, and alcohol gives a form of it too, as noted and celebrated in many country western songs.)
Having fulfilling and enjoyable work is a confidence builder. But it's important that your attitude toward yourself not be tied strictly to your job position and title because if you lose the job, you'll likely lose your self-confidence. One CEO told me about being on top of the world on Monday, getting fired on Tuesday, and by Wednesday feeling like a failure.
But back to the self-talk: the simplest, most honest, strongest mental verbiage that you can give yourself is to expect and assume acceptance of who and what you are. Oust your harmful internal critic. You are not below or above anyone's station. Between the Creator and the Constitution, you are equal to anyone. What you do with yourself with those facts is up to you.