Doing your best, School effort, Key to failure

It is no use saying, "We are doing our best." You have got to succeed in doing what is necessary.
~ Winston Churchill

School is a drill for the battle of life. If you fail in the drill you will fail in the battle.
~ Karl G. Maeser

I don't know the key to success, but the key to failure is trying to please everybody.
~ Bill Cosby