A Shattered Arm
The story is told of one of the pious whose neighbor, a skilled scribe, supported himself from what he earned in the practice of his art. One day the pious man asked his neighbor, "How are you faring?" "Fine," he said, "so long as my arm is sound." That very evening he shattered his arm, and he could not write with it for the rest of his life. It was Divine retribution for having placed his trust in his arm.
If a person obtains his livelihood through other individuals, he transfers his trust to them and comes to rely on them. But when his intellect matures, and he sees their deficiencies and their need for the Creator, may He be exalted, he transfers his trust to Him and relies on Him in matters beyond his control and in which he has no alternative but to surrender to the Divine decree.
(Chovos HaLevavos, Shaar HaBitachon, Perek Zayin)