Crime is terribly revealing. Try and vary your methods as you will, your tastes, your habits, your attitude of mind, and your soul is revealed by your actions.
Is there ever any particular spot where one can put one's finger and say, "It all began that day, at such a time and such a place, with such an incident?
I've always believed in writing without a collaborator, because where two people are writing the same book, each believes he gets all the worry and only half the royalties.
It's no good starting out by thinking one is a heaven-born genius- some people are, but very few. No, one is a tradesman - a tradesman in a good honest trade. You must learn the technical skills, and then, within that trade, you can apply your own creative ideas, but you must submit them to the discipline of form.
One must accept the fact that we have only one companion in this world, a companion who accompanies us from the cradle to the grave - our own self. Get on good terms with that companion - learn to live with yourself.
Curious things, habits. People themselves never knew they had them. [Witness for the Prosecution, also published in The Hound of Death and Other Stories.]