I read this and then I had to think for a very long time.

Right now you believe that your worth depends on your behavior. Metaphorically, you see yourself as an empty vessel that must be filled, drop by drop, with your achievements. You start out essentially worthless, a body that moves and talks. [... There] is no intrinsic value in life, only a potential for doing something worthwhile, something important.

The truth is that your value is your consciousness, your ability to perceive and experience. The value of a human life is that it exists. [...] You are a person who is trying to live, and that makes you as worthwhile as every other person who is doing the very same thing. Achievement has nothing to do with it. Whatever you do, whatever you contribute should come not from the need to prove your value, but from the natural flow of your aliveness. What you do should come from the drive to fully live, rather than the fight to justify yourself.

From the book Self Esteem by Matthew McKay and Patrick Fanning.