At 6:25 a.m. my alarm clock started blaring its annoyingly tinny chimes and my mind snapped to attention, one thought piercing me through the sleepy fog: I messed up.

You had one job, I thought to myself as I frantically rifled through my desk drawers looking for a pen and scrap of paper. I was in the middle of scribbling a hasty, yet heartfelt, note from a mythical being when a little head popped out of her bedroom doorway.

“Mom,” she said sleepily. “The tooth fairy didn’t come.”

Too late.

I changed the tone of my note in that second, then tossed the pen and paper down as stealthily as I could, and being a pro at this point at failing parenthood, made up something on the spot.

“Oh, sure she did,” I lied through my clearly adult teeth. “She left this note on my desk, see?”

My 6-year-old walked over, eyeing me suspiciously, then peered at the handwriting that she has yet to identify as mine. Amazingly, the note passed muster, and she grinned toothlessly at me. “I can’t believe she heard me at the table last night, mommy! She let me keep my tooth an extra day.”

And the crisis was averted.

Now, I had thought for a moment about telling her the truth because she’d mentioned me being the Tooth Fairy before and I thought she might have been ready. But I got three words into it, saw her face and switched back to the changed-note plan. Six is old enough to learn the truth, but not on a school day when we have 30 minutes to get ready. No one can pick their heart back up off the floor in a half an hour.

That night, my daughter was prepared. With the floodgates of communication thrown open, she had her own note to the Tooth Fairy at the ready. “Dear Tooth Fairy, Thank you. I have three questions. What do you turn tooths into? Do you turn big? How can you cary pencils? Your the best.”

I pored over this letter and realized I didn’t know the answers. I had always assumed the Tooth Fairy was big and so carrying pencils wouldn’t be an issue. I also had a vague thought that she turned teeth into stars, but couldn’t find anything to back that up. Regardless, because the Tooth Fairy is tied to no actual myth, that’s what I said. I also said she could turn big when she needed to and that she borrowed our pencils so she didn’t have to drag one around.

The Tooth Fairy is the weakest link. If fantastical beings were all on a game show, she’d be the first contestant to go home. Unlike her competitors, Santa Claus and the Easter Bunny, the poor Tooth Fairy has no coherent history. She’s not backed by religious institutions. She doesn’t have one root in truth. She is instead a hodge-podge collection of different myths and traditions from around the world, and while other countries have something like her in place, the Tooth Fairy’s main venue is the United States – where cash is king.

In fact, according to a study by credit card company, Visa, teeth are going for an average of $3.70 a pop these days. My kids still get a dollar, up from a quarter when I was a kid (when we didn’t ask questions).

But her lack of a back story isn’t the biggest problem here. The biggest problem is that she’s not a once-a-year figure. Children lose approximately 84,937,648,203,495,276,895 teeth in the span of three years or so, according to science.

The Tooth Fairy emerges as a key player in that first tooth loss, soothing anxieties over growing up, over losing a part of yourself, over change in general. We used her because my kids were devastated at the idea of losing their precious teeth. As the first tooth got looser and looser, they would spend hours devising ways to keep it in their mouths forever. And so we told them about the Tooth Fairy, and her presence allowed them to begrudgingly give up that first tiny tooth. There was much fanfare, much praise and much preparation for the Tooth Fairy’s arrival.

But by tooth four, seriously, it’s easy to forget. I have twins, so it seems like every two weeks I have to wait for them to fall asleep, write an adorable note and somehow scrounge up a dollar in cash because my kids don’t accept credit for some reason. And after they’re asleep, it’s kind of hard to remember the seventh tooth deposit that needs to be made sometime between 11 p.m. and midnight.

And that will be our downfall. That will tear the fabric of the entire mythological world we decided to build around our children when we decided to let loose that first bald-faced lie about Santa Claus before they could even talk. Kids are naive and hopeful, but they aren’t stupid. Enough Tooth Fairy stumbles and we’ll have to have a talk about the truth and how it’s the feeling of goodwill and happiness that keeps this from being a hurtful lie. That the Tooth Fairy exists, just not as a tangible being.

Once that’s out of the bag, Santa and the Bunny are on the chopping block. The crack in the rock-solid trust of parents saying ridiculous things will expand until it crumbles the keystone of childhood belief.

Maybe we were better off when the Tooth Fairy was first starting out as a mouse. At least then we could blame our neglectful forgetfulness on a furry, very much real, creature.

Darlena Cunha is a former television producer turned stay-at-home mother to twin girls. She writes for The Washington Post and Time and tweets @parentwin.