Your body needs food for energy. Include a little protein and some carbohydrates. Eat for energy. Get the right amount of sleep. Let the light shine in.
Exercise increases levels of feel-good chemicals called endorphins.
Stress and poor posture can cause you to breathe shallowly instead of inhaling deeply from the diaphragm. Spice up your life. Try something interesting, like a hobby, a date, a meeting with old friends. Have some fun. Remember the things you like and the people who make you laugh.