There's an old saying that goes, "Those who can, do; and those who can't, teach." At first blush, the sentiment behind this saying appears to be no more than an unjust criticism of the teaching profession. However, if we were to alter this saying a bit and apply it more universally, we can use it to identify a pattern of human behavior that affects all of us: Some think that they can do almost anything, while others think they can do hardly anything.