Well, actually life can be terrible at any age. As a child, you're always told what to do by other people, there are so many things you don't understand, you want things you can't buy, you're put in clothes you loathe, you're forced to spend time with distant uncles and aunts who mean nothing to you.
When you're middle-aged, you're loaded with ongoing responsibilities like bringing up children, looking after elderly parents, paying off a mortgage, building up a retirement fund, scrambling up the career ladder, coping with tyrannical bosses, maybe saddled with a huge overdraft.
Any age can be ghastly. But the real difference between one age and another is how much help and support you get.
Children have the support of their parents and relatives and siblings and teachers. They're surrounded by other people who want them to have happy and fulfilling lives.
The middle-aged are usually supported by a family network that helps with child-minding, ferrying children to school, giving parenting advice, providing loans and dealing with emergencies.
If they're lucky, older people will also have a family and friends to keep an eye on them, but they may not be so fortunate. Deaths may have wiped out their family and many of their friends and they may end up quite isolated and unable to get the support they need. They may struggle to keep their spirits up and get through their daily lives.
It's not old age that's the problem. It's whether you have a helping hand when you need it. Or preferably a whole bunch of helping hands.