And he might laugh, and sing, and be cheery while he was doing it.

But in the case of the worrier he not only pushes the rock up the hill, but he is beset with the dread that, every moment, it is going to roll back and kill him, and he thinks of nothing but the fear, and the strain, and the distress.
When one calmly considers, it is almost too ridiculous to write seriously about the needlessness and uselessness of worry; its futility is so self-evident to an intelligent mind.

Yet, because so many otherwise intelligent and good people are cursed by it, it seems necessary to show its utter uselessness.

These say: "I would stop worrying if I could; but I can't help it; I worry in spite of myself!" Don't you believe it! You doubtless think your statement is true, but it is nothing of the kind.

Worry could find no place in your mind if it was full to overflowing with something really useful and beneficial.