Shallow breathing prevents the body from getting enough oxygen. Many people fail to breathe deeply when they feel tense, which is one reason they may feel zapped at the end of a stress-filled day. “The general principles of correct breathing are to make it deeper, slower, quieter, and more regular,” says Dr. Andrew Weil, author of Healthy Living Weil. Doing so helps you force more oxygen into your cells, which slows heart rate, lowers blood pressure, and improves circulation, ultimately providing more energy. Weil suggests you do a simple breathing exercise twice a day or whenever you feel yourself losing steam: Put the tip of your tongue against the ridge behind your upper teeth. Exhale completely through your mouth, making a whoosh sound. Then inhale deeply through your nose for a count of four, hold your breath for a count of seven, and exhale through your mouth for a count of eight. Repeat for a total of four breaths.