I was West playing 4♠. Opponents led a ♥ and I cashed A♥, then AK♦ throwing my ♥ loser. I now took the opportunity to finesse ♠ and when South didn't cover my 10 I guessed right and finessed Q♠ but I still had two trump losers. Cash the A♠ and exit with a trump. South leads back another ♥. I ruff and exit again with a trump.
Now South has only clubs left, so forced to lead into my KQ. They cash the A♣. Contract made! I thought to myself at the time, nice end-play. But no! South could have defeated the contract by leading J♣. Then I can't avoid two club losers. So I was just lucky... .
Perhaps the contract can't be made against good defence. Or is there a way?