It's always too early to quit.
Well done is better than well said.
Quality is not an act, it is a habit.
Always desire to learn something useful.
To be a good loser is to learn how to win.
Be gentle to all and stern with yourself.
Problems are not stop signs, they are guidelines.
Who seeks shall find.
If you think you can do it, you can.
What you do today can improve all your tomorrows.
I'm someone who's done the opposite of whatever the received wisdom is, to keep your career going into your 50s.