Euphoria. What is it good for? Who knows? It's an overflowing of good feeling, intense happiness, and self-confidence. From the Greek: a state of well-being.
Yes, a state you can visit, but not live in. Maybe a state that descends upon you? Or is it a self-generated state - some particular combination of body chemistry, barometric pressure, the weather, the day of the week, or something else?
Probably best to just enjoy it, and not question it too closely. I have found that my euphoric states are usually followed by some kind of depletion, or dip in energy... so maybe it's just a forerunner of something bleak?
And when does euphoria tip into "mania" - an abnormally elated mental state? Who knows? There is a continuum, one thing bleeding into another and one state drifting into another. That's life.