Why the middle-aged are grumpy

Happiness in U-shaped:

Satisfaction with life starts to drop as early as a person's late 20s and does not begin to recover until well past 50, says Bert van Landeghem, an economist at Maastricht University in Belgium.

While young adults are carefree and full of hope for the future and the over-50s have come to terms with the trials of life, the research indicates that those in the middle feel weighed down by the demands on them.

This should be a daily duh! Your first childhood ends in your late 20s when your kids start arriving and you have to take responsibility for others. Your second childhood starts when the kids are grown up.