This is a case of "negative reinforcement". The term was created by B.F. Skinner, and it is about not doing something in order to avoid suffering or pain (physical or psychological). A good example of negative reinforcement can be seen in the movie "A Clockwork Orange", directed by Stanley Kubrick. The main character goes to a correctional facility where he's forced to watch violent movies while experiencing an unimaginable sensation of nausea. The goal of the institution was to turn him into a non-violent individual by conditioning his brain to associate violence with feeling sick to his stomach. In fact, after such experiment he wasn't even able to enjoy Beethoven's music anymore, since it was played throughout the whole "therapeutic" movie sessions. In Herbie's case, he could no longer eat his daily chocolate chip cookies, since he didn't want to get nauseated again. It doesn't mean he would necessarily feel that way if he actually had the cookies, but he refused to eat them anyway, since he'd already been negatively reinforced not to eat them.
Answer:
Be well rested so you can do your best.
It shows the doer of the action.It comes before verb and indicates this action or work is done by it/him/her etc.Ex.Susan switched off the lights. Who switched off the lights? The answer is Susan (subject of the sentence)
