It's always too early to quit.
The dog that trots about finds a bone.
The most effective way to do it, is to do it.
To be a good loser is to learn how to win.
Never complain and never explain.
Leap, and the net will appear.
Be thine own palace, or the world's thy jail.
Begin to be now what you will be hereafter.
Well done is better than well said.
By failing to prepare, you are preparing to fail.
As for everything else, so for a mathematical theory: beauty can be perceived but not explained.