When you're younger, it's all theoretical. It's all potential. As you get older, it becomes actual, and your life gets filled with unexpected complexity; some of it asked for, and some of it not. It becomes richer, I find.
Our own existence once presented the greatest of all mysteries, but. . . it is a mystery no longer because it is solved. Darwin and Wallace solved it. . . I was surprised that so many people seemed not only unaware of the elegant and beautiful solution to this deepest of problems but, incredibly, in many cases actually unaware that there was a problem in the first place!