One should deeply meditate on the fact that G‑d guides and gives life to the whole world, and to each and every one of us individually. This should remove worry from our hearts, for surely G‑d causes the best to happen, and this does not depend on us. The one thing that does relate to us is our free choice to study Torah and perform mitzvos.

This is not my invention, for this matter is simple and known to all. However, if this attitude is external to us, and when it comes to our actual conduct we act as if everything is contingent upon and controlled by us, this causes useless heaviness in our hearts and our lives. In contrast, when we are permeated with the belief that “G‑d is my Shepherd,” then even the body and the animal soul feel the “I shall not lack.”1

Igros Kodesh of the Rebbe, vol. 4, p. 189