A couple of lessons apply here. Mr. Market can change his mind in a hurry and in a big way, which is great news for investors who profit from volatility. In mainstream finance, price volatility is considered a bad thing, but for value investors it's a blessing; there would be no way to make money if prices didn't move!
Second, I didn't actually find this idea myself; instead, I read about it from other value investors first, as discussed here. Luckily, by the time I got to it, the price was still low, but that's not always the case.
To take advantage of Mr. Market's mood swings, make sure you pay attention to what other value investors are doing, and be sure to act fast, as you never know how long an opportunity will be available!
Disclosure: No position