Baal HaSulam, Shamati, Article 34 “The Profit of a Land”: Every form points to another [opposite spiritual] form. Thus, all the descents where one feels that he has come to separation [from the others and within them, from unification with the Creator] are an opportunity to discern between something and its opposite.
In other words, one should learn the benefits of the ascents from the descents. Otherwise, one would be unable to appreciate the importance of being brought near from Above, and the ascents that he is given…[as it is said:] “As far as Light excelleth darkness.”
After all, only from separation can we appreciate unity between us and esteem the attainment of our unity as the attainment of the Creator, of the upper force. We have to try to give the correct definitions: Separation between us is a descent, while unity between us is an ascent. Separation, meaning a state of descent should bring us the sensation of the absence of Light, whereas an ascent should be felt as the presence of the upper Light, the Light of bestowal and love.
We have to correctly interpret the spiritual properties, the spiritual definitions. Then we will gradually get used to them and will begin to see the upper spiritual value in the words so hateful for us today: “unity,” “love,” and “adhesion.”
Only then can one assess and regard the matter of adhesion, by which the delight and pleasure in the Thought of Creation can be acquired, being “His desire to do good to His creations.”
From Lesson 8, WE! Convention 4/3/2011