It dawns on one sometime between one's mid-Fifties and mid-Sixties. What dawns is the realization that your priorities have changed markedly. A milestone birthday is usually the trigger for reflection and the realization that one's earlier priorities had been overcome by new ones. The two sets of priorities were not like tectonic plates bumping up against one another with friction. The change is slow and subtle. Some examples:
Noisy restaurants. Step into the trendy new restaurant in any large city and you will find it packed with under-35s, has bare oaks floors, loud music, high-decibel talk and nothing to keep sound from bouncing off walls and ceilings. Young people like cramped, noisy restaurants and bars because these are part of the mating ritual (whether for one night or a lifetime). Conversation is irrelevant. The only reason to go to a quiet, romantic restaurant would be to propose marriage.
Older people, on the other hand, always prefer quiet restaurants because they like to dine with mates or long-time friends and exchange news and views about families, travels, the events of the day without having to shout.
Traffic. It is so congealed in and around most cities -- even medium-size ones -- that if one can avoid commuting from the suburbs to work downtown one does. One strategy is to live in the city and walk. I moved to a new office last year, a mile-and-a-half from home, and now walk to and from work. This means thinking ahead to allow enough time for a walk that is not at top speed (which defeats the purpose). Also, no more speeding up one's pace to make it through the crosswalk before the signal changes. Instead, I slow down and enjoy the red light. After all, it only lasts 70 seconds. There are multiple benefits to walking: the people parade, shop windows, fresh air, exercise and a bit of schadenfreude when you see those stalled motorists gnashing their teeth.
Fewer choices. As one gets older, there is a strong desire to simplify life's smaller things. For me, this means finding vendors and services that, while not perfect, are consistent and generally good. Thus, I take most flights on the same airline; use the same rental car company, the same long-distance carrier, the same bank, the same Internet service provider. They all seem to improve with age -- mine. In a world filled with computer-driven activities and their plethora of passwords, reducing as many as possible of life's quotidian aspects to simplicity is both important and satisfying.
Taking politics in stride. Important issues are still worth fighting for, but you no longer fret and fume over the outrageous statements or behavior of politicians. Politics is their business and they are as interested as you or I in surviving. They are forever calculating the effect of this or that legislative initiative on the opinions of their constituents and shaping their positions so as not to alienate enough of them to get them kicked out of office at the next election. Besides, in Washington, one learns when working on issues that today's adversary may be tomorrow's ally -- and vice versa. So, better to find the humor and irony in the meanderings of Congress than to let one's blood pressure rise.
Youth dreads milestone birthdays and makes much of how "awful" it is to turn, say, 30 or 40. This probably masks an unspoken realization that the cherished belief of the young -- that they will live forever -- is not true. Looking back from the other side, one has a very different perspective. In fact, it is not hard to draw the conclusion that each passing decade has been better than the last.