Discarding a losing card on a losing card has been the fundamental element of play since the days of Whist, Bridge Whist and Bridge. The concept is simple, ....
Contrary to the usual practice, today's hand was a battle between Mr. Dale and Mr. Champion, the former trying to give away a trick and the latter trying to avoid winning it.
Why do some players recognize the correct play only after it is too late? Sometimes it is discovery of the laction of the opponents cards. Many times it's becuase a tempting and good line of play was easily apparent.