The practice of relaxing the muscles of the body will bring rest to the body and to the mind also. The tension of the muscles will be relieved. People who know the science of relaxation do not waste any energy. They can meditate well.
Take a few deep breaths and then lie down flat on your back as in Savasana. Roll on to one side and then relax as thoroughly as you can do. Do not strain the muscles. Roll on the other side and relax. This is naturally done by all during sleep.
There are various exercises in relaxation, for the particular muscles of a particular part of the body. You can relax the head, the shoulders, the arms, forearms, wrist, etc. Yogins know the science of relaxation thoroughly.
When you practice these various relaxation exercises, you must have the mental picture of calmness and strength.