Diamonds are nothing more than chunks of coal that stuck to their jobs.

The quip reframes transformation as the product of endurance: coal becomes diamond only through sustained pressure over time, so human excellence is portrayed as the result of sticking with difficult, unglamorous work. By calling diamonds “chunks of coal,” the line demystifies success—implying that extraordinary outcomes often begin as ordinary material. The phrase “stuck to their jobs” adds a moral of diligence and reliability, suggesting that talent or luck matters less than persistence. It also functions as a rebuke to impatience: valuable results may require long periods of strain before they become visible.