"Once you’ve found the pleasant sensation, you fully shift your attention to it. If you can do that, the sensation will begin to grow in intensity; it will become stronger. This will not happen in a linear way. At first, nothing happens. Then it’ll grow a little bit and then hang out and grow a little bit more. And then eventually, it will suddenly take off and take you into what is obviously an altered state of consciousness.
In this altered state of consciousness, you will be overcome with rapture, euphoria, ecstasy, delight. These are all English words that are used to translate the Pali word piti. Perhaps the best English word for piti is “glee.” Piti is a primarily physical sensation that sweeps you powerfully into an altered state. But piti is not solely physical; as the suttas say, “On account of the presence of piti, there is mental exhilaration.” In addition to the physical energy and mental exhilaration, the piti will be accompanied by an emotional sensation of joy and happiness."