Time is the best killer.

I would like it to be said that I was a good writer of detective and thriller stories.

Ah, but life is like that! It does not permit you to arrange and order it as you will. It will not permit you to escape emotion, to live by the intellect and by reason! You cannot say, 'I will feel so much and no more.' Life, Mr. Welman, whatever else it is, is not reasonable. [Hercule Poirot]

Bitterness leads nowhere. It turns back on itself. It is the eternal cul-de-sac.

There hung about her the restrained energy of a whiplash.

What they need is a little immorality in their lives. Then they wouldn't be so busy looking for it in other people's.

Curious things, habits. People themselves never knew they had them. [Witness for the Prosecution, also published in The Hound of Death and Other Stories.]