When interacting (read playing) with infants, objectives are very clear in our head. We must make them laugh, even at the cost of looking foolish. And we must, at all possible cost, avoid them from crying.
Yet somehow, we manage to forget those objectives when dealing with adults.
Strive to delight people. Be it family and friends, your customers, employees, business associates, and definitely even the unsuspecting and often invisible-to-us support staff (janitors, security personnel, peons, etc.).