Consider two roommates, call them A and B, with very different drinking habits. A drinks to excess on a daily basis, while B drinks only on rare occasion.
Suppose now, despite an eclectic cast of wine and sundry harder stuffs rotating through the pantry, a single beer survives an unusually long time in the fridge.
Now, this brand of beer is a particular favorite of B's — if B were to drink a beer, this would be it. As each day goes by, however, A observes the beer is still there. With each passing day, A 's certainty that B is off liquor for good grows.
B, for his part, grows to expect the welcome presence of the beer in the fridge. Each day arriving home from work B notices the beer. B thinks A 's interest in this particular brand must have waned, and with each day B's expectation that the beer will be there waiting for him grows.
ending 1: That Tuesday, B experiences a particularly trying day at the office. Filled with frustration, he decides to finally drink the beer. On the way home, he becomes filled with anticipation at the rare treat to come. When he arrives home, he discovers that A has drunk the beer.
ending 2: That Tuesday, A gets off work early. He's in a good mood, relaxed, and feeling breezy. Arriving home, he's in the mood for lighter fare then he's tended toward recently in hours of stress. He notices the beer. Although previously he'd refrained from drinking it in deference to B's tastes, he'd recently notice a pronounced drop in interest on B's part in booze. With a clear conscience, A tells himself waste not, want not.