unforced errors

Unforced errors are mistakes made without pressure from an opponent—failures that result from one's own misjudgment rather than the difficulty of the situation.

The term comes from tennis, where a player hits the ball into the net or out of bounds when not challenged by a difficult shot: She lost the match on unforced errors.

The phrase has spread to politics, business, and everyday life for self-inflicted blunders: The campaign's unforced errors cost them the election.