The Baal Shem Tov was once in need of financial assistance and approached the home of someone from whom he was hoping to gain some support. He knocked on the man's door but left immediately before the homeowner could answer. Seeing the Baal Shem Tov in the distance, the homeowner chased after him and, after ascertaining the reason for his visit, offered him his needs. He asked, "If you needed me so much, why did you just knock and leave?"
The Baal Shem Tov replied: "In truth, sustenance comes from G-d. However, there is a verse in the Torah that states: '...and G-d will bless you in all that you do.' Thus in order to fulfill the directive 'in all that you do,' I just needed to perform an action such as knocking on the door. Once I had done my part, I was sure that G-d would do His."
The lesson to be learned is this: One must trust that his sustenance comes only from G-d, and that all man's exertion in sustaining himself is nothing more than a vessel in which G-d desires and is able to bestow His blessing.
Sichos Kodesh, Devarim, 5734