There is physical evidence of the body's response to doing good. Endorphins are released in the brain when you do something for someone else. Doing good really feels good.
When you really concentrate, you will get a sense of expansion. You will feel that you are larger person than you are physically, as if you become a person two or three sizes bigger than your ordinary physical self, and that you are flowing with all your being toward the object of your concentration. Whether it is a physical thing or an image that you are concentrating on, your whole invisible person will be in movement.