I recall learning that the Arizal would sweat profusely when learning nigleh and that this was related to removing the klipot. I cannot recall the source for this; does anyone know?
There is a famous dictum: 'lo ba'shomayim he', meaning that after the torah was given at Sinai its rules, mandates and precepts are determined by man and not dictated by heaven. An example is when ...
It says in Sforim that one shouldn't learn Kabbalah from any of the students of the Arizal except for R' Chaim Vital (as they didn't understand the Arizal properly). I have never seen such a worry ...