Bidding is about discussion with partner, as I have pointed out earlier. Declarer play is about taking care of business on your own. If you discuss things properly with partner, you will end up in the correct contract. Then, if you get to play the hand, you can make sure that you fulfill the agreement you have with partner. If partner has cooperated and you have reached the best spot, don't let partner down by sloppy declarer play.
Let's take a look at Board 7 from Week 08 Wednesday night's play:
Board 7 Dealer E All Vul