Sounds like Mark TwainBetter to remain silent and be thought a fool than open your mouth and remove any doubt.
Beauty may only be skin deep but ugly cuts clear to the bone.
Steal a little and they put you in jail, steal a lot and they make you king.
The difference between stupidity and genius is that genius has its limits.
A friend to all is a friend to none.
Don't look a gift horse in the mouth.
Leave sleeping dogs lie.
Discretion is the better part of valor.
You can lead a horse to water but I'll never suck it's ass to make it drink. (my version)
I can explain it to you but I can't force you to understand it.