Old and relevant enough?

"Wise men speak because they have something to say; Fools because they have to say something."

Plato

Good, cheap, fast. Pick two.

Older
 

If you see your enemies fighting, try not to interfere.

There are a terrible lot of lies going about the world, and the worst of it is that half of them are true.

Men occasionally stumble over the truth, but most of them pick themselves up and hurry off as if nothing ever happened.

Success is the ability to go from one failure to another with no loss of enthusiasm.

Winston Churchill