Baal HaSulam says that only by uniting in the group is it possible to unite with the Light. Otherwise, the Light does not "perceive" us since we need to become similar to it. And when we unite together, we are like a plug that enters an outlet due to the exact opposite equivalence of form. The Light can already influence us in all the empty spaces within us and correct them by making them similar to it according to our desire during the studies.
In order to organize the right form of studying the articles of Baal HaSulam, his elder son, Rabash, created a method of connection to the writings of his father. If we use it, we can be sure that we will realize everything correctly.
We shouldn’t forget that all the Kabbalists talk about the need for a group in which we implement this method and make ourselves similar to the Light. A person is unable to do this alone. Even if one exists at a great spiritual height, he will be unable to rise further or even remain at the degree that he achieved without unification. Even if he has already reached the 124th degree, he will be unable to rise to the final, 125th degree if he works alone.
Remember the story of Rabbi Yosi Ben Kisma who said that if he were to leave his students, he would be unable to advance and would lose the level that he already possessed. The fact that they were small and he was their teacher was irrelevant; what was important is that they were together.
If there is unification, there is equivalence to the Light. Without unification, there is no equivalence. This is a completely mandatory condition.
From the 4th part of the Daily Kabbalah Lesson 9/16/10, Lesson for Commemoration of Baal HaSulam’s Passing Day