How can a person know when they are a success? For most people success is measured by three "Ps": prosperity, power, and privilege. But these are inadequate measuring tools.
Here is an insight: why not leave it for the next generation to decide whether you've been a success or a failure? After all, if you are still around, you are still in the race.
Sometimes people who look like successes end up proving to be failures. And sometimes people who never see the fruit of their lives end up being the means by which others achieve great things in the next generation.
My whole life I have been standing on the shoulders of others who went before me and made my success possible. On the surface it looks like I've been more successful than they were, but it's not really true.