https://medium.com/illumination/understanding-confidence-and-how-to-build-it-in-your-career-and-life-7b1e449aa265?source=friends_link&sk=4f1531b82288de8ed3c84265fe86db40
To obtain confidence, you must be engaged in life. You must have done something to have earned it.
Good lines @Bill Abbate
My confidence increased when I was able to provide a job to my ex-boss in my current organization. I had to convince the CEO about the impeccable capabilities of my ex-boss. Voila, he was interviewed and got the job instantly.