A cure for thumb-sucking

A few weeks ago, I was doing my sandal-season pedicure and Allie asked if I would paint her fingernails. I don't love fingernail polish, so I was trying to come up with a plausible excuse to convince her not to paint her nails. So I said, "Well, Allie, you won't be able to suck your thumb if you have fingernail polish on it."
Being the quick-thinking highly-motivated little girl she is, she immediately said, "Well, I won't suck my thumb." So, after a few minutes of negotiating, my girl & I came up with a plan.
Every day that she didn't suck her thumb, I'd put a new color of fingernail polish on her nails. I was pretty sure this deal wouldn't last long.
15 days later, she's still going strong.
Ladies & Gentlemen, I found a cure for thumb-sucking.
Get yourself a highly-motivated, driven girl who knows what she wants and is willing to work for it!

I let her pick out 2 colors.

Every night & every nap, she'd habitually bring her hand to her face as she laid down, and then I'd see her remember her goal & stop her hand before it got to her face. I found her asleep like this several times -

This experience showed me a great side to Allie's personality. She recognized her goal, really worked hard and she was determined to be successful. Good traits.