Tranquility is a necessary component for contentment. Tranquility is also the proximate cause of insight. This is the primary reason why a meditator is taught concentration practice prior to learning insight or vipassana meditation. Only a calm mind can relax into its true nature: radiant and pure.
Humans are blessed with breath; an ever-present biological function that acts as a conditioner for the body and mind. The quality of breath has a direct influence upon the quality of mind and body. When we are stressed or fearful, breath is fast, short and often we even find ourselves “not breathing.” When we are content, happy, and restful, breath is slow, long, gentle, or deep. You may have noticed that when you feel anxious, if you put your attention on how breath is and slow it down or deepen it, often anxiety abates.
When we bring awareness or what is called “relaxed attention” to breath in a focused way, breath itself becomes a gateway to calmer states of mind and body. Staying with breath long enough, leads to calm, which leads to interest in the mind, and joyfulness in the heart and body. Eventually, the excitement gives way to a contentment, which arises from the direct experience of the mind knowing its own radiance and clarity.
If radiance and clarity is the true nature of mind, why do we not experience these qualities of mind all the time? Primarily this is due to the presence of habitual thought-generated mental hindrances, such as unwholesome desire, anger, laziness/inertia, restlessness, and doubt that grip the mind and pull it away from experiencing its own true nature.
In concentration meditation we learn to stop feeding the hindrances by starving them. We train the mind to stay present with an object like breath, which naturally leads to calm, clear, and contented states of mind. Continually choosing over and over again, to turn away from distressful states of mind and turn toward the experience of breath eventually gives us the confidence, to turn the mind toward the hindrances, and stay present with these distressful states of mind to engage in the inquiry of vipassana meditation practice.