My opinion really on the topic of being the best in something, is that it probably has some relationship with your genetic makeup. When people look at geniuses like: Einstein, Euler, Gauss, Tao, etc. These people from a young age were intrigued in their fields, or knew the area they mastered.
Everybody can reach their full potential with some push and guidance, say specialist maths you can put in a heap of effort and get say a 40. You have people like TT who have more than a desire to get above 40, they are passionate in that area.
E.g. A really good particle accelerator can accelerate an electron to 99.99% the speed of light. Accelerating an electron to 60% isn't too hard, 80% is a little harder but still managable, 90% even harder, 95% is even harder than that, 99% is when the electron is basically is at it's full potential speed, 99.9%, 99.99%, then 99.999% requires that much energy that the effort needed to increase it's speed outweighs the effort and it has reached it's limit.
You could look at a student who got a 49 in a subject and they may say with more effort I could have got a 50, or someone who got a 99 they would say with more effort I could have been a 99.05. There has to be a point when you can be happy with what you achieved.
People settling for so called "mediocre scores" or the saying "it's better to live life wanting what you can't have, opposed to having what you don't want", maybe what seems mediocre to one person is a goal to another. We are the best at knowing what we can achieve, what our limit is.