“If at first you don't succeed, try, try again. Then quit. No use being a damn fool about it.”
"Insanity: doing the same thing over and over again and expecting different results."
These two quotes mean that if you're failing at something hopelessly and getting the same results every time, you should just stop wasting your time and give up whatever you're doing, or try something different. If you continued whatever you were doing, you would receive little to no change in your results, even if you try REALLY hard.
In other words, they're trying to say that if it's too hard, whatever "it" may be, just give up.
I know. "Real inspirational". But it's true!
Wise up children!