Listen to the signs; they give the answer
Henry Ford said, "Whether you think you can, or you think you can't - you're right." It helps to have a positive attitude. Anyone who thinks he cannot make a contract will usually not be "disappointed."
In today's deal, though, the key decision comes at trick one. What should West lead against four spades after the given auction?
North showed a game-invitational hand with exactly three-card spade support. Note that it was advantageous that North could show his good diamond suit, so that in a borderline case, South would have been able to make an informed decision. Also, North-South could have stopped in two spades. Using two-over-one game-force, North must start with one no-trump forcing, then jump to three spades over South's two-heart rebid. This would be doubly less satisfactory.
Suppose West leads the club queen. South wins with his ace and takes dummy's diamond winners to discard his club loser. Then declarer plays a heart to, say, his jack. West may win and shift to a trump, but South takes that with dummy's 10 and tries a heart to his king. West wins again and leads a second trump, but declarer wins in hand, ruffs a heart, ruffs a minor, draws West's last trump and concedes a heart. South loses only three heart tricks.
Now go back to trick one and have West lead a trump; and play another trump every time he wins a heart trick. Then declarer cannot ruff a heart and loses four tricks in the suit.
When strong in declarer's side suit, lead a trump.