Did you ever hear the tragedy of Darth Mauseloch the Wise? I thought not. It's not a story the Jedi would tell you.
Let me paint you a picture. It's Miller time. The game is on. Darth Mauseloch has just come home from a long day of ruling the galaxy with an iron fist and he just needs to unwind. Unfortunately for you, Darth Mauseloch has an oral fixation and his favorite way to unwind is to chew on the wiring in your living room wall, which means that even though it's also Miller time for you, you don't get to relax yet. Why not?
Because when you hit the light switch on your way in the door, nothing happens. Well, shit.
You go to the closet and grab a new bulb. You pick up the step ladder from the garage but then remember the little catch that keeps it from splatting you on the floor is busted, and so you have to fetch a chair from the kitchen instead. Great. That's one yak shaved bald.
You unscrew the old bulb and plug in the new one, cursing the fact that these damn things cost like twenty bucks now and can't be thrown in the garbage but have to be disposed of in a special unicorn dick factory because they contain mercury or magic pixie dust or whatever the fuck lobbyists love these days... Anyway, new bulb in place. You hit the switch again, and this time you cross your fingers.
Boom! Light comes on. Problem solved. Everything's good now except one small detail...
There was never anything wrong with that bulb.
What actually happened is that your friendly neighborhood Darth just got his fix and is now relaxing on the couch with a cold one. He's busily swearing at the referee and you haven't even taken off your boots yet. He wins.
Darth Mauseloch just fucked you over and you don't even know it. And, honestly, you can't know it. You've done your work on the basis of the scientific method: you made an observation, you developed a hypothesis, and you tested your hypothesis. To the best of your knowledge, your hypothesis is correct--but of course it isn't, because there is a variable here that you're not aware of.
So, basically, the lesson here is that mice fucking suck.