Constructive criticism is like spinach: We may not like it ourselves but are sure it would be wholesome for others.
East doubled North's Stayman bid of two clubs to guide West's opening lead, and the defense began with three high clubs. West threw a low diamond, and East got out with a diamond. South then led the jack of trumps: five, three, six. He guessed well to lead the queen next, pinning East's 10, and claimed his game.
West was ready with the spinach. "You goofed," he told East. "Lead another club at Trick Four. If he ruffs low or discards, I ruff with the eight, forcing out the ace, and my king scores. If instead he ruffs with an honor or with the nine, I discard and get a trump trick."
Few players like constructive criticism. (Most of us can barely cope with constructive praise.) Bridge is an ego trip, and criticism spoils the journey. Moreover, before you give partner a can of spinach, be sure your analysis is unbiased by the result.
Did East goof? A good defender imagines a hand for declarer that will let the defense prevail. East "gave" South K-Q-x-x in spades and A-x-x in hearts. Then South loses a heart -- unless East leads a fourth club, conceding a ruff-sluff.
The winning defense required West to hold K-8-x or Q-8-x of trumps; East's defense needed West to hold Q-x-x-x of hearts.
East's defense was reasonable; it just didn't happen to work. West's criticism was so much broccoli.
A 7 4 3
K 10 6 2
10 8 7
K 8 5
9 7 5 4
J 8 6 5
10 9 4 3
A Q 9 4 3
Q J 9 2
A Q 3
A K 2
J 5 2
South West North East1 NT Pass 2 Dbl2 Pass 3 Pass4 All Pass
Opening lead -- K