It's always better to show sportsmanship and class in victory and defeat rather than rubbing a victory in your opponent's face or being cocky in the final seconds of a victory.

Things like that come back around and if you don't believe us, you will shortly.  A Madden player by the name of Tripp Warrick shared this video of a game against a player by the name of StLunatic31432.

With 21 seconds left to go in the 4th quarter, Tripp was trailing by nine without any timeouts and it looked like all hope was lost.  Fortunately for him, his opponent got cocky and called a timeout for him to stop the clock after he picked up a first down.

With 8 seconds to go, Tripp kicked a field goal to cut his opponent's lead to 6 and then this happened:

His opponent recovered the onside kick, but decided to lateral the ball thinking he had the game won.  Tripp picked up the ball and went the other way to score the TD and win the game.
Everyone can learn a couple of lessons from what happened in this game.  First and foremost, it's never over until it's over and, as the old saying goes, karma is (we'll let you fill in the rest).
(H/T: FTW)