One thing I do
The first element [in the secret of Paul’s incomparable life] is the element of wholehearted concentration. “One thing I do”—not a dozen things, not even two things, but this one thing I do. No life can be very great or very happy or very useful without this element of concentration. Decision is energy, and energy is power, and power is confidence, and confidence to a remarkable degree contributes to success. Turn to any realm that you will, and the vital meaning of concentration stands out in all human life in the most striking fashion.