Teenagers

The thing that irked me was the lack of sensible advice. When you have a new baby there are literally thousands of books to choose from and I armed myself with a statistically valid sample. As I recall the Marina Petropoulos book was most useful, probably because it was the most sensible. My own mother warned me not to take any of them too seriously since "the baby hasn't read them dear, so doesn't know what she's supposed to do"
But there was nothing to cover teenagers. No wait, I think The Exorcist probably started as a self-help book for parents of teenagers but the studio thought demonic possession would be a more rational explanation.

Yup, teenager in full hormone-induced rage. Image link here
 
The good times are wonderful but obviously you don't need help with those, it's the wild hormone-swings that make you wonder how the population explosion happened in the first place.
Then you also have to deal with those infuriating mothers who swear their children are sweetness and light, and would never (insert human failing here). I took them with a pinch of salt, I've always been deeply suspicious of people who pretend their lives are perfect, they're either willfully unaware or getting help from chemicals
So now that I have survived two teenagers (the second one has a few months to go) I can say, with some authority, that there are benefits to allowing them to live, difficult as that decision may be at times. It's also wonderfully heartening to know that while there are times you may not like them much you always love them.

Oh yes, and locking your makeup away in one of those petty-cash boxes works a treat for mothers of teenage daughters.