It's always too early to quit.
Things do not happen. Things are made to happen.
Quality is not an act, it is a habit.
Know or listen to those who know.
Without hard work, nothing grows but weeds.
The secret of getting ahead is getting started.
Leap, and the net will appear.
By failing to prepare, you are preparing to fail.
What you do today can improve all your tomorrows.
Who seeks shall find.
If you always put limit on everything you do, physical or anything else. It will spread into your work and into your life. There are no limits. There are only plateaus, and you must not stay there, you must go beyond them.