We will be relentless in our pursuit for perfection. We won't ever be perfect - but in the process we will achieve greatness.
Mental toughness is many things. It is humility because it behooves all of us to remember that simplicity is the sign of greatness and meekness is the sign of true strength. Mental toughness is spartanism with qualities of sacrifice, self-denial, dedication. It is fearlessness, and it is love.
Greatness is not attainable, but in the pursuit of it, you can achieve excellence.