What I regret most is never having known what it is that I wanted to do in life. What I admired and envied most in my schoolmates is that at very early ages most of them knew what they wanted to do in life and how to get there.
To this day, if I were granted the power to choose any profession and be the best at it, I would not be able to confidently make a choice.
While this failing has not caused me any serious depression, it is a life-long regret.