In Sefer Chofetz Chaim al Hatorah, a story is related by the melaket (Parshas Beshalach in He’aros Maaseh L’Melech) that depicts how bitachon creates parnassah:
There once were two brothers in the city of Bialystok who bought a large forest in partnership and made a lot of money. They were busy selling the trees they had already cut down, and still had more trees left to chop down, when they had the opportunity to buy another forest. This second deal had the potential of making them very rich. One of the brothers opposed the idea, reasoning that he had no intention of entering into new business while he was still busy with the forest they had already bought. In contrast, the second brother was firm in his opinion that this was an opportunity that should not be missed.
The brothers decided to present their claims to the Chofetz Chaim, who was then in Bialystock for a meeting of the Vaad Hayeshivos. They agreed to do whatever he advised.
When they presented their arguments to him, he told them that he had no knowledge or understanding of such matters, and that he was unable to advise them. However, after they pleaded with him and told him that the matter would lead to a dispute between brothers if he didn’t help them, he said, “I am not a prophet nor the son of a prophet, but I will tell you a story from which you can take a lesson:
“There once was a man who had a barrel full of wine. He used to pour the wine from it through a spigot at the bottom of the barrel, and this took ten minutes. Someone told the owner of the barrel, ‘Make another tap in the barrel, and the wine will pour through both of them in five minutes!’ The owner of the barrel replied, ‘I would listen to your wise advice, if I could extract more wine from the barrel than the amount of wine that is in it. Since I can’t do that, why do I need a second tap? Boruch Hashem, I have enough time to wait five more minutes...’”
The brothers now understood that buying another forest would only be like making another spigot in a barrel. They wouldn’t get any more parnassah out of it, so what’s the point?
The melaket of the sefer adds: “Two years ago, while I was traveling from Warsaw to Vilna, I met one of the brothers. He told me that it was miraculous that the Chofetz Chaim advised them not to buy the second forest because someone else ended up purchasing it and losing a lot of money as a result.”