... And the limits are personal, and can vary immensely, unfair as it might be. Some people high jump 2.45 meter, or design a spaceship that flies to the moon, whilst most people couldn't do this in a thousand lifetimes

Usually, though, people don't do something for long enough to get close to their limits, so, generally in life, all this doesn't matter that much, does it.

And to keep trying and doing what one enjoy is good advice :-)