When you quit, you may find that everything feels a little off-kilter. Try to be aware of what your body is telling you. If you feel overly tired, don't push yourself. Your body and mind are trying to adjust to a normal state; that won't happen overnight. Don't take on more than you can handle. Eat a healthful diet, drink plenty of water, and get plenty of rest and exercise.
Manage stress so it doesn't build. Take little breaks for yourself throughout the day. A few deep breaths, a stretch to relax your muscles, or a quick walk in the fresh air can help reduce stress.