There are a lot of important things to remember when you are refereeing a soccer game, with the most important probably being DO NOT RUN INTO THE PLAYER WHO HAS THE BALL.
Credit: user foxinyourbox on r/soccer
This is how Real Madrid lost their lead against Granada. They're going to be really, really mad.
Update: Real Madrid won because the guy who got picked here, Luka Modric, scored an incredible goal.