But even people who don't "succeed" by the standards of the modern society are fortunate. Many "failures" live in developed countries, or in countries where the standard of living has improved dramatically over the last 100 years. They are fortunate not to have been killed when they were young. They have many things to be grateful for.

Why should the "successful" people be grateful any more?

And, furthermore, what if you define success in a different way? Perhaps all that Linus has forever wished in his live was for a specific girl to love him, and he just wasn't that "fortunate"?