Nice explanation, Jees.
Google has its own worldview and is highly biased towards materialist, reductionist, pharma industry compatible sources when it comes to plants and energetically/spiritually involved topics.
So we have seen two different concepts here. First is roughly "asceticism" for the general purpose of purification and connecting and aligning with God/Higher Consciousness. Second is a specific practice to ally plants spiritually (dieta). Shamanic training involves both these elements, the former perhaps lacking with brujos.
For me the first concept (asceticism) is a science (mostly forgotten in today's world), a very old one in human culture and also a timeless reality pertaining to the relationship between the physical world and spirit.
OneIsEros's example is another one of a person having healing abilities which is said to not lead a "pure" life (because he was drinking alcohol?). İt is a complex matter and having certain healing powers are possible with imperfect adherence to purity. The person must have paid a certain price to gain/integrate healing abilities. Nothing is given for free. God given talent still does not allow to having a life dedicated to the pleasures of the ego AND having a manifested healing/spiritual vocation in this life.
Also, the emphasis on psychological healing is found in the modern world and it is not necessarily a part of traditional shamanic practices which focus on working with spirits. My own convinction is that for healing our own minds, hearts, spirits etc, adhering to a diet when engaging with psychedelic plants is very important.
İf you want to transcend your ego/the energetic matrix that make up your personal limiting world, then you have to let go of your ego and it's desires, your comfort zone, your routines. The deeper energies and going into the subconscious require exceptional focus and thus discipline is required.
If it bursts outside it's confining cages, science will eventually accept and understand energetic and spiritual phenomena. For now, just focusing on the physical dimension, it has recently discovered how fasting triggers a purification process in the body. I have come to understand that physical and spiritual purification go hand in hand.
The consciousness of plants is a constant source of information for medicine, alimentation, and art, and an example of the intelligence and creative imagination of nature. Much of my education I owe to the intelligence of these great teachers. Thus I consider myself to be the “representative” of plants, and for this reason I assert that if they cut down the trees and burn what’s left of the rainforests, it is the same as burning a whole library of books without ever having read them.
~ Pablo Amaringo