Friends: 25 Lessons That Completely Changed Your Life

21. Be Careful Whose Sandwich You Eat

Because someone, somewhere in your office might already be having a terrible day.

20. You Should Be Nice To Everyone At School

It might be way too late for most of us, but the fable of Will Colbert (Brad Pitt) in "The One With The Rumour" proved that nastiness to your fellow students can lead to scandalous rumours that you have both types of genitals, and "The One After The Superbowl" proved you should never humiliate a girl in public, especially if she grows up to look like Julia Roberts. But then again, maybe be careful you're not TOO nice, no matter how drunk you get in college...

19. The Best Way To Enter A Room

You probably don't have a gigantic porcelain dog to ride, but there's a good chance that you wanted one because of the potential for perfect entrances.