Many players get sloppy in their declarer play.....just like my partner did the other day. All he did was fail to consider a 5-0 trump break. He held: AKQJx...x...Axx...AKJx opposite my dummy hand of 10xx...xxx...xxx...Q10xx. The contract was 4S and the opening lead was the Ace of hearts, followed by another. Initially it looks an easy contract with 4s, 4c, 1D plus the one heart ruff at trick 2. So when my impetuous partner ruffed the second heart, he was doomed after the subsequent discovery of the 5-0 trump break. He was now forced to concede two diamonds and a club ruff !
What should he have done ?.... Well, given the possibility of such an extreme break happening, he ought to have guarded against it.....by simply pitching his 2 diamond losers on the inevitable heart force. This meant that 4S was an absolute certainty despite the adverse trump position. The loser on loser principle would have ensured ( without any undue alarm ) the last ten tricks courtesy of 5S, 4C and 1D.