From the Letters to His Son — Lord Chesterfield

Dear Boy, Know the true value of time; snatch, seize, and enjoy every moment of it. No idleness, no laziness, no procrastination: never put off till tomorrow what you can do today. Whatever is worth doing at all, is worth doing well; and nothing can be done well without attention. Take the tone of the company you are in, and do not pretend to give it; be serious, gay, or even trifling, as you find the present humour of the company. Wear your learning, like your watch, in a private pocket; and do not pull it out and strike it, merely to show that you have one.