I have gone through life thinking that I am basically OK, and a pretty capable sort of person.
I have obviously had my hang-ups, like not being able to recite Wordsworth, or touch my nose with my tongue, but I did well at school, I have had jobs that I have loved, and overall I have felt able to hold my own.
That is... until I had children. According to my six-year-old daughter Betty's favourite book about the human body: 'By the time you are six years old, your brain is as big as an adult's.' I can certainly vouch for this.
Betty has started excelling in certain activities of late. And this, combined with her starting to ask me some pretty tricky questions, is seriously beginning to make me question my own abilities.
Bedtimes used to be a time of calm and loveliness with my kids. We used to snuggle down after their bath and read about fluffy bunnies and funny dragons. These days however, with Betty's favourite thing being the detailed workings of the human body, it has become a time of apprehension for me.
On a nightly basis, I find myself fielding questions like: "What are the cells in our muscles called?" or "How long are ureters?"
"Cell and ureter what?" I say nervously. "Oh it doesn't matter, I'll go and ask Daddy," and off she flounces, shooting me a frustrated look as she goes. I must admit though, it's quite fascinating to be learning about parts of the body I never knew existed.
Biology was never my strong point. But unfortunately it isn't the only area where I am beginning to feel like a complete moron.
Last week, it was a beautiful sunny day and we all sat in a pub garden having a lovely relaxing lunch. "Come on Mummy, do some cartwheels with me," Betty called, as she elegantly somersaulted around the garden, with a belly full of scampi and chips. "I am 39 years old," I protested. "I am far too old for cartwheels."
"Could you do them when you were younger though?"
"Erm, not really," I replied.
The truth is, I spent much of my childhood trying to master how to do a bloody cartwheel, but I was utterly crap. I could barely do a clumsy roly-poly without twisting my neck or spraining a wrist.
Betty also has a flair for languages, and music, and being able to touch her nose with her tongue, and sometimes doing all three at the same time.
Feeling that I am lacking in certain basic areas, Betty decided that she was going to give me some lessons. But she despaired very quickly when she discovered that I didn't even know where Middle C was. The same with Spanish, and me not being able to get past: "What is your name?"
Thankfully, I'm not alone in being outsmarted by a small child. My friend Lucy tells me: "Ben came home from school spouting gibberish the other day. 'Stop talking nonsense and concentrate on eating your tea!' I snapped.
'But mum, I was asking if I could have some more juice in Welsh,' he moaned, before collapsing into a heap of (justified) tears."
And another friend told me about her daughter Ellie, who asked her if she could take a dead baby sparrow she found into school to show everyone.
"Fine," I said, "but can you tell me what sort of baby bird it is, so you can tell them at school if they ask?"
"Yes Mum, of course I can, it's a dead baby bird."
It is only a matter of time before Betty and her peers decide they have had enough of their inadequate parents and go off to start a new community somewhere, where things are done properly and competently. Perhaps they will invite us to come and visit now and then - we could be like their special pets.
In the meantime, I'm off to practise my cartwheels.
Do you feel your children are testing you - and finding you wanting?