Real secret of success

Mark Twain "Roughing It" (Polish title: "Pod gołym niebem")

We never touched our tunnel or our shaft again. Why? Because we judged
that we had learned the real secret of success in silver mining--which
was, not to mine the silver ourselves by the sweat of our brows and the
labor of our hands, but to sell the ledges to the dull slaves of toil and
let them do the mining!