In To Have and Have Not, Marie (Lauren Bacall) asks Harry (Humphrey Bogart), “You know how to whistle don’t you? You just put your lips together and blow.” A career was launched and Bogart—and millions of other guys—were left speechless. That’s just how powerful taking a deep breath and then exhaling purposefully can be.

When you breathe in your lungs fill with oxygen, nitrogen and water vapor, along with a smidgen of argon. Oxygen passes from your lungs into your blood and (via the heart) to all the tissues in your body. Sensors in your brain, the carotid artery and the aorta detect your blood’s carbon dioxide and oxygen levels and adjust your breathing rate as needed. Without thinking about it, you breathe 17,000-23,000 times a day!

But if you become aware of your breathing—and practice deep breathing techniques—you can reduce your stress response, promote better sleep and boost your immune strength