Konchog1 wrote:If you try to do [Completion Stage practices] without proper preparation-which means a thorough grounding in the graduated path-and without a stable deity practice, you will lose your mind. I mean that quite literally. You really need to know what you are doing; otherwise all sorts of things can start to happen. If the energies move into a wrong area, moving them back again is incredibly difficult. There are many mediators who have gone completely crazy because that have not followed the practices correctly or tried to take shortcuts.
-Tantra by Geshe Tashi Tsering pg. 117
All types of Mahamudra and Dzogchen are completion stage practices, still they are taught very openly and I doubt there were many who have lost their minds because of that. Or perhaps what was meant are specific wind related techniques? In that case, we're back to the subject discussed a few pages back.
"While teachers of the middle way, mind only, transcendent wisdom, mantra, and other schools may have their own assertions, the fulfillment of those intentions is the same. There is not a single thing that is not contained within mind."
(Gampopa to Düsum Khyenpa, in "The First Karmapa", KTD Pub, p254)
“If you recognize the world of appearance and existence as the mind, realize the mind itself as empty, and have no grasping at the superiority of your realizations — this is the ultimate view."
(Chegom Dzongpa, in "The Book of Kadam", Wisdom Pub, p609)