Admitting the ball was out when nobody saw it is braver than winning the point.

Calls nobody else can make are the ones that reveal what winning is worth to you. Taking the point you were not owed leaves a small mark, and enough of them add up to a person who cannot quite believe their own results. Saying it out loud costs a point and buys back the meaning of the score.

Make the honest call in the small game where it does not matter, because that is where the habit forms. Say it immediately, before the calculation starts. Nobody will make a fuss, and you will remember it.