Believing I deserve

I wonder what makes one person feel their life is less worth more or worth less than another. As a child I always felt that my life was disposable at the cost of another’s as I wasn’t really adding much value? I used to fantasise that if there was a situation where someone should stand up and have to say “ok, I’ll take the bullet” I would be the one?
Now as a mother I know my children’s life is definitely more valuable than mine TO me. However, pondering back to that feeling as a child always feeling that “others” mattered more. I believe this could be a gender-based school of thought, or perhaps swayed by the marketing / advertising world as to who and what counts and the rest of us are just peripheral? Does this come from our parents? Our society? Our cultures? Our schools? Our environments?