"Until a man selects a definite purpose in life, he dissipates his energies and spreads his thoughts over so many subjects and in so many different directions that they lead not to power, but to indecision and weakness.
With the aid of a small reading glass, you can teach yourself a great lesson on the value of organized effort. Through the use of such a glass, you can focus the sun's rays on a definite spot so strongly that they will burn a hole through a plank. Remove the glass (which represents the definite purpose), and the same rays of sun may shine on that same plank for a million years without burning it."
- from Napoleon Hill's 'The Law of Success', Chapter 1