No idea why this would be downvoted, this is absolutely true - there is not just one version of what a successful life looks like. Deciding how you define success is a principle part of forming yourself as a person.
While this sounds great, it's a bit like when people say you can "choose what to believe". You cannot, in fact, choose what to believe. You either believe something or you don't. Similarly, with feeling successful, you either do feel that or you don't. It's not really under your control.
But what you can do is realise that things aren't always under your control so not to worry about them. Instead just concentrate on things you do have and things you can do. You have the power to be useful to society so do that. You have the power to do good things so do it. How you feel doesn't really matter.
But what you can do is realise that things aren't always under your control so not to worry about them. Instead just concentrate on things you do have and things you can do. You have the power to be useful to society so do that. You have the power to do good things so do it. How you feel doesn't really matter.