When I started playing poker, I didn’t worry a whole lot about reading poker players-I just played the cards I had and hoped that they would work out for the best. As I matured as a player, I made it a point to observe the other players around me and play the man more than the cards.

I was in a home game early on in my poker career and I was watching the guy across from me as he placed his chips. He had two distinct ways of pushing money in-he would either toss them in carelessly or gravely add his chips to the pot. After watching a few hands play out, I came to realize that he was acting the same way every time, and it made sense: when he acted upset he had a great hand, and when he acted cocky he was holding garbage. It was a ridiculous tell, and I was definitely going to be taking advantage of it. I could have used it all night if I hadn’t made one crucial error.

After deciding that the tell was reliable, I used it to re-raise him and buy out a pot that he was trying to bluff. As I raked in my cash, I gleefully announced that I’d read him like a book-I described his tell and how I used it to everone at the table, including the player in question. Just as I finished gloating, I realized that I just gave up my advantage-the player, now aware of his mistake, changed up his play and my tell was useless.