You have to be fast on your feet and adaptive or else a strategy is useless.
We suffered a terrible blow on 11 September 2001. We responded with fear and anger. A fight-or-flight response is adaptive in any species. For us, given our power, fight was the only response we could imagine.
Play is a uniquely adaptive act, not subordinate to some other adaptive act, but with a special function of its own in human experience.