It was on a very rainy day that the Baal Shem Tov was sitting in
yeshivah with his students - deep in prayer and study - when a passing wagon got stuck in deep mud. The gentile wagon driver poked his head in the window of the
yeshivah and requested help. Seeing that the wagon was sunk knee-deep in mud, they told him that they did not have the strength to successfully retrieve the wagon. The gentile responded with a Russian expression: "Able, you are able. You just don't want. And when people don't want, they pretend that they are not able."
The Baal Shem Tov explained to his students: "We must learn from the wagon driver's statement how to better serve G-d. The Torah tells us we must always work to enhance our learning - but sometimes one believes that he doesn't have the ability because he feels tired. The truth is, we must learn from this person's response that, 'Able, we are able,' for G-d grants us the strength to accomplish all good things. But because we are influenced by our negative drives, we tell ourselves that we are not able."
Sichos Kodesh 5720, 15 Tammuz