Terence Mckenna tells a story of his brother getting stuck in a trip for many days after a big dose...take that with however much salt is needed. For most people it will probably be the weirdest experience of their lives, but they'll also probably wake up fine the next day. It's hard to describe how strange a shroom trip can get, even at light doses you can be delving into your psyche and having mystical experiences that are so powerful, that I think at those extremely high doses you'd lose all sense of self but unlike Alice, you have no narrative to bring back; the Cheshire cat consumes you & vomits you out in a million particles of confused mind-pieces, shattered and disparately swirling deeper into the wierdness.