According to the study, set to be published in the journal Social Science & Medicine, happiness follows a U-shaped curve: It is highest at the beginning and end of our lives and lowest in-between.
The researchers found that the peak of depression for both men and women in the U.K. is around 44 years of age; in the U.S., women on average are most miserable at age 40 whereas men are when they hit 50. They found a similar pattern in 70 other countries. (LINK)
From a participant point of view, i would say that life seems to be more of a marathon then a race. and in a way we are not racing our peers or friends, we are racing against ourselves of yesterday. and in each circle the prizes and winners are different. when we were 16 the one with the coolest car and hottest girlfriend, in your mid-30s perhaps it is the vacations and job that is gonna win, so and so on. it seems to most that these races are being counted by others, going in circles to gather as many points as possible, in todays social media your post create a mirage of sorts of everything going well, while just under the fragile surface, all surfaces, a wreck of problems await.