When I was growing up I heard from everyone that I could choose who I wanted to be when I grew up. Being lightly-autistic, I took this far more literally than it was intended.
I really believed that with hard work any person could achieve the same results as anyone else, and sheer determination could make up for any natural deficits a person may have. For several reasons I decided I wanted to be a great artist, and worked my very best to make this a reality. After 15 years of constant failure I came to realize that I didn't have the necessary talent to be even a mediocre artist, much less a "great" one (great in this case meaning pleasing to my own tastes).
Now I am 29, surrounded by piles of sketchbooks I hatefully filled with worthless drawings, and regretting I wasted my youth. I have spent my life preparing for a vocation I will never take part in.
Eventually I came upon the idea of determinism, and the lack of free-will it implies. After I accepted that free-will is an illusion, I saw my failures in a different light. I am still bitter, but my life-long self-hatred has been replaced by indifference.
I believe this notion that people have the power to make their own destiny is incorrect, and in some cases harmful. Using basic critical thinking it is easy to see that no one would choose to be miserable, or poor, or stupid, or lazy. But people still cling to this notion of a fair life, of being rewarded for effort, and of some kind of control over their own destiny. The result is that those whom are successful look smugly down on those whom are not, because they assume those people have not put in the effort necessary to succeed; and the unsuccessful people end up hating themselves for being failures, believing they are at fault for their own misery.