Answer: It is because the discrepancy between what is desired and what is in reality invokes suffering. In this case, you want to advance, but you feel inferior compared to the state you would like to be in.
But on the other hand, these are positive sufferings. They teach you to move forward correctly. It is therefore forbidden to immerse into them and to sit and cry, but you must implement them correctly.
Question: So, the revelation of evil involves suffering no matter what?
Answer: No. It depends on how you perceive it. If you do not feel the difference between what you want and what you now have as suffering, you will not advance. But this is not the path of suffering.
The path of suffering is when you are unconsciously in them and do not know how to move and what to do. All of humanity is in this state.
Only people who study the wisdom of Kabbalah are aware of the sufferings that they receive and can use them to aim themselves toward the purpose of creation. They ascend above the sufferings and even feel it as sweetness, as guidance toward the desirable goal.
From KabTV’s “Fundamentals of Kabbalah” 11/18/18