It's easier to see the mistake on someone else's paper.
Don't expect a stranger to wipe your nose.
Sometimes it's smart to be scared.
It's not enough to be able to spell "magnificence" in your bedroom. You have to be able to spell it at the microphone during the spelling bee.
One thing you can't pretend to be is funny.
It's easier to throw sticks on the campfire than to try to restart it when it goes out.