Charles Dickens, rejecting an invitation from a friend:

“It is only half an hour’ — ‘It is only an afternoon’ — ‘It is only an evening,’ people say to me over and over again; but they don’t know that it is impossible to command one’s self sometimes to any stipulated and set disposal of five minutes — or that the mere consciousness of an engagement will sometime worry a whole day … Who ever is devoted to an art must be content to deliver himself wholly up to it, and to find his recompense in it. I am grieved if you suspect me of not wanting to see you, but I can’t help it; I must go in my way whether or no.

via “Creative People Say No”