Rav Nahman said there is a evil inclination in the service of God of going overboard. It is hard to know what are the exact parameters of this. I for one took myself to study of the Ari while at the Mirrer Yeshiva in N.Y., and this certainly can be considered to be going overboard. After all, right at the Introduction of the Eitz Chaim, you have the warning and oath of Rav Chaim Vital that no one should look at his book who has not fulfilled the set of enumerated conditions. Take a look at them, and you will see that no one who has looked at that book can possibly have fulfilled those conditions in the last couple hundred years. No one is fasting from after Shabat to the next kidush.[Not to leave the subject in the middle, let me say that the issue still is unclear to me --since after all I think that this learning helped me in many ways. Still, I jumped in too soon, and still needed to do a lot more of Shas]. At any rate, I do think that learning the Ari for some time helped prepare me for the Land of Israel, and the amazing light which shines there. So I would have to say that Rav Shmuel Berenbaum was right when I asked him about this sort of learning. He said, "First finish Shas." I said, "I already did." He said, "Do it again." [Of course when Reb Shmuel said, "First Finish Shas", he did not mean the way some do it. Rather, he meant in depth (beiyun) with Tosphot, Maharsha.]