In a shamanistic scenario, working up the strength of intent and will to deliberately break a taboo and drink pee is part of the psychological procedure, and intensifies it at that level... [What are you, a baby? "Ewww, icky-poo, I dont wanna... Wah! Wah!"] You have a reason to, to trip deeper and harder, you know it wont hurt you, so TAKE CONTROL OF YOUR OWN REVULSION AT A META LEVEL AND TURN IT OFF AND GO BEYOND IT!
Many many "vision quest" processes incorporate some deliberately frightening and/or revolting act you must develop the strength to control your own fears/instincts before The Spirit deems you worthy of granting its special secret revelations to. Like an initiation experience... Like having to do horrible stuff before being admitted to the frat, its all similar: you are proving you are strong and worthy and fully in control of yourself in ALL WAYS, far beyond the ordinary mortal, and thus are deserving of special access to privileges and secrets. Understand?
Theres also a symbolic idea, like the snake that is symbolic of The Universe, swallowing its own tail, you are "consuming yourself" by drinking your own pee, like the universe creates itself as a dream, then enters into the dream and experiences itself, like drinking of its own substance, in order to learn more about itself. The ritual honors that as well, and takes you into that on a conscious and subconscious level. Understand?
But if you are not ready for all that "strength and self-control and symbolic offering nonsense", and cannot get over "Ewww, yucky!" responses, young grasshopper

, and just want a stronger druggy buzz, just make extra shroom simmer extract and redose with that once you start to feel the initial "inebriation" setting in, that will work just as well on a simple drug-level to give you the deepest effects.