What is Your Best?

So I have been thinking lately like I usually do and want to put up a question for you guys. Define doing your best? You know when they say that I can't take a another step or do it one more time; certainly you can take another step and then you might say I can't take another step but you probably could take another step and so on and so forth.


So if your best is gauged at your top level at which you can not do anymore, and you tell what your top level is by what you have done in the past how can you tell what your best is when you are doing something that you have never done before?


So what is your best?