"When i do good i feel good. When i do bad i feel bad."

Abraham Lincoln

I think this means that you should choose to do good things so you can have good vibes. Felling good can help your self off steem. And can help you sleep at night knowing you did the right thing. Felling good about yourself can help you during a test  or during any sport tryouts. Felling good helps you because you have a higher chance to not doubt yourself. And doubting yourself is not the thing you should do.