You have done remarkably well to get to 7NT but that is just the time for extra caution. It is a sad but true fact that it is at such moments of intense excitement or anticipation that attention to small detail flies out the window. It would be all too easy for declarer to say, ‘I have three tricks in the majors and five tricks in each of the minors unless I am really unlucky.’ So he has, but there is a danger. Suppose you win the first trick in dummy and throw a useless heart from hand. You can no longer make the contract! Why is this? When you try to cash five diamond tricks, you will find them blocked whenever one defender has three of them headed by the jack – quite a possible scenario. You will have to cash the ace-king-queen and win the fourth round of the suit in hand. That leaves you a trick short. Of course, you can easily avoid this problem by keeping a level head and discarding a diamond and not a heart at trick one