Hanhagos HaAdam of the Rebbe Reb Melech (Rabbi Elimelech of Lizensk) continued...
5. Sometimes learn with great awe a few of the holy writings of the Arizal. This must be done with awe reverence and fear of Hashem. In the previous generations they had holy and lofty souls and would guard themselves from the time of their youth. They were ready and properly prepared to study the Kabalistic wisdom.
However in our lowly generation with our base physical lusts and desires you must cleanse and purify your soul from all sins. Once you see that the evil inclination is no longer inciting you and trying to cause you to sin and lust after the silly vanities of this world as he once was, you can study these holy writings more often. Hashem should merit us to refine and purify our holy thoughts with truth and complete sincerity. He will open for us the gates of wisdom in understanding the holy writings of the Arizal.
Those who are clothed in the lusts and desires of this physical world and in the vanities of time who study such texts may however, suffer detrimental consequences heaven forbid.
(See Maor veShemesh to parshas emor “The cult of Shabbtai Tzvi (the false messiah) may their name be blotted out that lived in those past days became heretics as a result of this lack, they studied Kabbalah while their bodies were in an impure state.”)