It is in fact God (and the side of holiness) that gives power to the Sitra Achra (the Other Side / the forces of evil) to be able to rise itself over the side of kedushah (holiness). This is in order to give us the opportunity to overcome it and ultimately cast it to the ground and humble it. This is the goal.
The idea we discussed in the previous lesson about shouting at the Sitra Achra, calling it a variety of derogatory names in order to subdue and humble it, is brought in the Chumash itself. In the story of the spies, the spies return with a bad report about the Land. With that, they convince Bnei Yisrael that it will not be such a good idea after all to enter the land (filled with giants etc.) Having brought Bnei Yisrael to lose all hope in entering the Land, and even worse in not believing that God could actually bring them there and destroy the 31 kings, God shouts at them declaring that He will make certain that their corpses will remain in the desert as they travel and they will not indeed be allowed in the Land.
Suddenly, they change their minds and say that they are prepared to enter the Land after all. But it is already too late and the decree is sealed.
The Alter Rebbe tells us this story in order to make us aware that the plan of the Sitra Achra is to take us away from serving God as we should. Sometimes, the only way of getting rid of it is to literally shout at it, alarming it with such a fright, that it will leave us alone so that we can get one with dealing with matters of holiness and happiness.
We begin Chapter 30 taking things one step further. Here, the Alter Rebbe is about to take us on another journey that will help us to understand more about our own lowliness and the importance of realising who we really are. When we can do this in all honesty, we can reach high levels. In fact, it is through acknowledging our own lowliness that we can rise up to very high levels.
The Alter Rebbe quotes a Mishnah from Avot that instructs to be humble before every man. He will tell us that this applies to every single person. That we need to be aware that no matter where we are in our lives, perhaps we have not worked on ourselves sufficiently. Perhaps we have not even reached the level of the lowest of the low in our service of God. Ultimately, it is through this that we will be able to ascend. We will learn more in depth about this in our future lessons.