As Forrest Gump once proclaimed, “Stupid is as stupid does.” By that measure, I haven’t been demonstrating a lot of smarts lately—and it’s not the first time.

When I was about two, Mom told me it was a bad idea to put my hand on a hot burner. I decided to see for myself. When I was about nine, I got excited and started jumping up and down on a folding chair. It folded. Time after time I’ve bitten off more than I could chew, burned the candle at both ends, thrown caution to the wind, and failed to use my head. Stupid is as stupid does.

So how about you? Do you know that feeling of beating your head against concrete and wondering why it hurts? Well, here are a few words of wisdom to remember about your own cluelessness:

“To forget one’s purpose is the commonest form of stupidity.”

—Friedrich Nietzsche, philosopher

“A word to the wise isn’t necessary—it is the stupid ones who need all the advice.”

—Bill Cosby, comedian

“Creativity is the sudden cessation of stupidity.”

—Edwin H. Land, inventor

“The stupid neither forgive nor forget. The naïve forgive and forget. The wise forgive but do not forget.”

—Thomas Szasz, psychiatrist

“Two things are infinite: the universe and human stupidity. And I’m not sure about the universe.”

—Albert Einstein, scientist

“Idleness is the stupidity of the body, and stupidity is the idleness of the mind.”

—Johann G. Seume, theologian

“The trouble with the world is that the stupid are cocksure and the intelligent full of doubt.”

—Bertrand Russell, philosopher

“The question now is: Can we understand our stupidity? This is a test of intellect, not of character.”

—John King Fairbank, historian