The Zohar, Introduction, “The Second Commandment,” Item 203: …Then fear clings to both sides, the side of good and love and the side of harsh Din, and she is included in them. If fear is included on the side of good and love, it is complete love, as it should be. …since there is love only in two sides—GAR and ZAT de Bina—and love is incomplete on either of the two sides unless there is fear in each of them, since there cannot be Hochma without Bina, which is love without fear.
This explains the completion of all of our work: How to attain love in Kelim (or desires) of bestowal and then also in the receiving Kelim. In essence this is already the full correction of creation in Malchut, which unites with Bina so much that it attains Keter, where its bestowal is perfect in all of its Kelim.
Question: What is fear?
Answer: Fear is the first commandment, meaning the first correction we have to go through. It is a person’s worry and fear: Is he able to attain bestowal to the Creator? This is fear: Will I attain this? Am I capable of this? Will I ever desire this? Then a person has work.
As a rule our work is aimed at maintaining what we have attained. Baal HaSulam writes about this in Letter #2 from 1920:
Wisdom only comes with experience. I advise you to awaken inner fear that the love among you might cool down, even though the mind rejects this view of things. You should go through the trouble anyway. If someone has the opportunity to add more love, but he doesn’t do it, this will be deemed a flaw.
It’s similar to how a person gives his friend a great gift. The love for his friend that becomes revealed at the moment of the action in the heart of the gift’s receiver, is not similar to the love that remains in his heart when the action is completed. Day by day it cools down, until it may reach total oblivion to the gift of love.That is why the person who received the gift has to invent tricks so as to look at it with new eyes every day.
Spirituality is built on the fact that we do not forget the inspiration that we have attained and we constantly keep the same inspiration while expanding it more and more.
From the 2nd part of the Daily Kabbalah Lesson 2/13/11, The Zohar