Externally, Guhyasanas, resemble asanas (poses) but they go beyond. They defy many of the commonly accepted physical alignment principles. The body surrenders to the innate flow of the primal energy, the Kundalini.
The euphoria attached to Samadhi is beautiful. It is many times addicting too. The student knows his limitations so he could easily get out. Once or twice in this lifetime is enough. To chase it could lead to a painful downfall. He needs to come back so he could share this wondrous spiritual journey.