Answer: Zivug is merging of two spiritual objects that are not opposite to each other and are able to unite according to their equivalence of form, intention, and purpose, similar to how two people unite in partnership or marriage.
Suppose there are two people who have a common spiritual goal. They are in constant opposition and confrontation with each other due to the force of breaking that rules between them. But they discover that they are unable to achieve this goal individually. If I advance on my own, I face an immovable obstacle. If the other advances on his own, he also faces a barrier.
What do we do then? In that case, I nullify my ego, and he nullifies his. In the degree that we succeed in doing so, we are able to unify as one. In this measure, we reach the goal.
This is the Creator’s condition since the goal is achieved only in mutual connection of all; after all, the goal itself is bestowal. Do you wish to reach it? Go ahead! Cancel your ego, and by doing so, you will build a Kli (a vessel) for bestowal. To the measure you do it, you will become filled with the Light of bestowal.
But it happens on one condition: if I nullify my ego and the other does the same with his. Hence, I strike my ego (Hakaa) and the other strikes his, and as a result, we perform mutual unification (Zivug de Hakaa). I perform a strike within me, at my ego, but I perform a Zivug with the other, outside of me.
Now, a question arises: Why then does a Zivug take place despite the fact that even after striking my own ego, I do not wish to unify with the other? It happens because by rejecting my ego with a strike, I draw the reforming Light, which pushes me toward unification, Zivug.
From the 3rd part of the Daily Kabbalah Lesson 12/10/10, Explanation of the Article, “Preface to the Wisdom of Kabbalah”