Sometimes reversing a truth or proverb can end up with another truthful, and if not that, at least witty saying. Below are some:
A master of all trades is jack of none.
Those who teach, can.
After the calm comes a storm.
Don't feed the hand that bites you.
He who laughs longest, laughs last.
No island is a man.
While there's hope, there's life.
Who wins dares.
Time wounds all heels.
Let lying dogs sleep.
Better never than late.
The cat killed curiosity.
Too many broths spoil the cook.
Fondness makes the heart grow absent.
The love of evil is the root of all money.
I'll post some more later. If you have any send them by note or publish as a comment here.