on Anne R. Allen:
A term used in scoring tennis, “unforced errors” are not caused by the actions of the player’s opponent, but they’re the responsibility of the player him/herself. S/he is caught wrong-footed, out of balance, unable to return the serve, incapable of making the winning shot.
The concept of unforced errors can also be usefully applied to writers. Unforced errors are the self-inflicted harm we do to ourselves.