He doesn't feel successful because he doesn't identify with any of the stuff he's doing. He always feels like what he's doing is a product of his environment, or someone else's idea. If he had set out to become a lecturer at Stanford and definitively achieved it, then he would feel successful. But his experience is that he stumbled into it, he doesn't feel like that's who he is or even really what he wants to do. So it doesn't feel like a success, it feels like a passing accident.
Yeah,what I mainly got from his post is that the author suffers from low self-esteem.
And you shouldn't compare yourself to him. People are not born equal, he had his own unique upbringing and environment. He was surrounded by genius, the cool kids, thus his view are such. And you have your own unique situation, probably was far less lucky than his so what's the problem?
By his standards, I'm worth less than a handful of dirt. While I have achieved some modest level of financial freedom, I didn't do anything as cool as that guy yet. And if I do some day, I'll remember to be thankful for it instead of whining publicly about not being Bill Gates.
For some people the realization that you're never done, that there is always something cooler to do, is apparently very depressing. Personally though, I'm glad it's that way. As long as you're healthy and capable the future is wide open. I find this much more inspiring than the idea that somewhere there is a big cosmic finish line waiting just for you to fall short of.