Best one-line advice?

[kc-steve]

From a National Lampoon magazine in the 1970s, . . .

"You can pick your own friends,
and you can pick your own nose.
But YOU CAN'T PICK YOUR OWN FRIEND'S NOSE."

 

[BigMike782]

Don't $hit in your own cornflakes.

 

[Groovy]

A drill sergant yelled this one at me when I was 18:

"Things will get better! Things will get worse! Things won't stay the same!"

Tru Dat!