Answer: It goes without saying that we pray for a friend because by doing it we want to transfer our strength to him.
Such a prayer does not necessarily have to be in joy, although prayer for a sick person still includes some joy because you rejoice that you want to give part of your health and strength to your sick friend.
Question: How do we check that the whole body agrees to this prayer?
Answer: It is impossible to check by the clock. Gradually, you will have an inner need, such as Kelim (Vessels), in which you will understand what state you are in, whether you are closer or further from the Creator.
Comment: After the fact, I already see that for some time, I was in other thoughts and not in the thoughts about a friend.
My Response: In that case, you should regret that the Creator pulled you out of connection with Him, gave you some pleasures in other thoughts, and thus, you distanced you from the Creator. Now, you begin to understand this and want to be closer to Him.
From the Daily Kabbalah Lesson 10/29/23, Writings of Baal HaSulam “Lishma [for Her sake]“