Happiness is something we feel. Peacefulness is something we feel. They are emotions that we feel.
The emotions we feel are largely a result of the thoughts we think. Just as chronic stress can cause hypertension, which has been directly linked to disease - chronic relaxation and calm have also been linked to health and healing.
When The Body Controls The Mind
Many of us turn to Yoga for stress release.
When the body is holding tension as a result of stressful thinking, worried thinking, angry thinking or thoughts of sadness, abandonment, betrayal - often the body tension maintains, and even encourages more reflection on past troubles... which, in turn, creates more stress and tension in the body. In this way - the body is 'living in the past', and sending signals to the brain to think in a way that matches the feeling. We get caught in a feedback loop.
Yoga can help break the negative feeling feedback-loop. It can open the body to better feelings, which opens the mind to better thoughts - creating better emotions - which, in turn, relax the body.
But, if we leave the yoga class and begin to think about our troubles in the same way as before - soon the thoughts bring up negative emotions and bring the body back into a state of hypertension... and the body is again in control of the mind.
When The Brain Controls The Mind
The human brain can imagine things so vividly that the mind responds as though the imagined is actually real. For example, we can sit in an empty room - think about out troubles, and feel negative emotions... just through thought alone. We can also recall fond memories and feel uplifted emotions... just through thought alone.
If we are to maximize the benefit of Yoga practice, we can take advantage to the post-workout relaxation by intentionally practicing thoughts, memories and imagined circumstances we desire... just through thought alone.
At first, a general mantra may help extend the calm experienced after Yoga. Repeating very generalized positive intentions while taking deep slow breaths can be a powerful way to 'interrupt' the habit of returning to negative memories of yesterday and to postpone negative anticipations of future events that may be tied to past negative experiences.
May I Be Happy, May I Be Healthy, May I Be Peaceful
By repeating this mantra, you will begin to build the intention that the meditative feeling of a Yoga class can be carried forward into the rest of the day. Just as repeat yoga practice will slowly condition the body to become stronger and more flexible, eventually permitting more vigorous poses to be expressed - repeating simple mental thoughts to generate better feeling thoughts will eventually permit more detailed mental movies that will generate more specific and vivid emotions... just through thought alone.