Do Your Best is a phrase I have heard many times. As a youngster I was a cub scout in Royal Oak, Auckland. Famously the scout motto is DYB DYB DYB.
But more importantly, it was a phrase my dad used all the time. He never said, "Try you best". Instead, it was, "Just do your best". That is enough.
So, I grew up with that phrase and it helped form my approach to life (the universe and everything).
As Ryan Holiday says (in Discipline Is Destiny) why wouldn't you do your best?
As in:
Why are you holding back?
Why are you half-assing this?
Why are you so afraid to try?
Why don't you think this matters?
What could you be capable of if you really committed?
When I ask my students to set goals, I always combine it with a question about their commitment level - if it's not at the highest - then they need a different goal.
Whatever job I've had I've always aimed to do my best. I would take it particularly hard, if my commitment level was ever questioned, because 'anything less is to cheat the gift' (Ryan Holiday):
The gift of your potential
The gift of the opportunity
The gift of the craft you've been introduced to
The gift of the responsibility entrusted to you
The gift of the instruction and time of others
The gift of life itself.