I can't profess to explain what you saw, but if it enabled you to experience a profound sense of release (and presumably move forward in your life), do you need to analyse it any further? These places are intensely spiritual, and spiritual things reveal themselves in strange ways. The fact you know you don't ever want to be there in the dark again suggests it was something a little more than just an experience of mist.

And it didn't hurt you, so enjoy the new future! :0)

t'chops