Breathing exercises are by far the best and most efficient and sustainable daily practice that can help you to outsmart stress as it can reaset (Return to Ease) instantaneously the negative response to challenges which have a detrimental effect on health and happiness.
Level I: To begin with Inhale ± 4 seconds Exhale ± 4 seconds Repeat for 1 to 3 minutes.
level II: When level I becomes automatic Inhale ± 5 seconds and imagine the sun warms your body Exhale ± 5 seconds and spread the warm through every cell of your body Repeat for 1 to 3 minutes and smile.
Level III: When level II becomes automatic Inhale ± 5 seconds and imagine the sun enters your heart Exhale ± 5 seconds and spread the warm from the heart to every cell of your body Repeat for 1 to 3 minutes (with your hand on your heart) and smile.
Heart rate variability (HRV) is the physiological phenomenon of variation in the time interval between heartbeats. It is measured by the variation in the beat-to-beat interval (WIKIPEDIA).