Passion has little to do with euphoria and everything to do with patience. It is not about feeling good, it is about endurance. Like patience, passion comes from the same Latin root: pati. It does not mean to flow with exuberance, it means to suffer.
The peacefullest times I remember were as a kid laying down drowsily in the backseat of the family van at night on road trips while my dad drove, and mom slept in the passenger seat. I've never known a greater sense of safety since those times.