I learned that lesson in my first full-time job as a sportswriter at the Tarrytown (NY) Daily News.

I covered, among other teams, the Sleepy Hollow High football team in North Tarrytown, and would try and predict the outcome of the games. If any of you have followed my NFL picks in recent years in Newsday, you know that's not an easy proposition, even at the high school level.
Anyway, in my first week on the job, I had to handicap the Sleepy Hollow-John Jay game at John Jay in Cross River, NY. If I'm not mistaken, John Jay had won the Class C championship the year before, and had a fairly decent program for a number of years. So, I picked John Jay.
Of course, Sleepy Hollow won the game.
But it wasn't until after the game that I realized how much my prediction had upset/motivated the Headless Horsemen of Sleepy Hollow. After it was over, a squatty nose tackle named Marty Fine came over to me and started screaming.
"Glauber, you son of a *@!@#$%, you no good !@#$%$@, we showed your @!#."
Fine must have railed at me for a good 60 seconds more, and I'm thinking, "What in the world is with this guy?"
Football is with this guy.
There is little doubt in my mind that Sleepy Hollow coach Bruce Thomas referred to the prediction in the newspaper to psyche up his guys. After all, on page 1 of most coaching manuals, there's usually a reference to using any means necessary to make your players believe the world is against you. Why else would Fine have reacted so angrily afterward? But it was a quick lesson in learning how passionate people are about football, and I've carried it with me ever since.
So ...
... Go Giants!
... Go Jets!
PS: I saw Marty Fine about 10 years ago at Giants training camp - he was an assistant high school football coach at the time - and he came up to me and asked if I remembered him from his days at Sleepy Hollow. I told him I could never forget.
If you're out there, Marty, I still haven't forgotten.
PPS: Thomas was one of the most gentlemanly coaches I've ever come across, and he was a true leader of young men. He retired years ago, but not before helping hundreds of kids enjoy a tremendous athletic experience.
He was also a pretty funny dude. At the end-of-year sports banquet, he was invited to the dais by athletic director Jack McCleery to say a few words. McCleery, also a terrific human being and a fine administrator, was wearing a dark green plaid suit that was ... well ... not very stylish, let's say.
"That's a nice suit you've got there, Mr. McCleery," Thomas says. "What awning did you fall through to get it?"