Tranquility is a state in which we are fully aware of the rise and fall of our thoughts. We know what thoughts arise at this moment and what will come up next. All these are clear in our minds. In other words, our observation is sharp. The process of dealing with distress is the process of practice.
We need the Dharma to make our heart healthier and purer. To achieve this better state of being, we should pursue happiness rather than sensory pleasures.