When I say: “There is none else besides Him,” it means that I accept upon myself a certain function in the world and not just go with the flow, living one moment after the other, telling myself to “let it be.” On the contrary, each instant I focus my desires and thoughts on how to correct my connection with the world and strive to find in it a single governing force. This effort of mine is regarded as “If I am not for myself, who is for me?”
Suppose I get sick and am going to see a doctor, but while doing so, I don’t just tend to my animate body; rather, I think about how I add everything to this one force. After all, the physician, the medicine, and I are all parts of the integral system. The doctor is managed by the Creator, and the medicine was discovered because of Him. In other words, I must connect everything that seems to me as existing separately from each: the doctor, the medicine, my sickness, and myself to a singular source.
And later on when I recover, I must say that all of it from the start was unified. The Creator simply turned the circumstances so that I would unify them within myself and see His oneness.
From the Daily Kabbalah Lesson 2/18/2011, Baal HaSulam, Letter 16, 1925