Look under the bed. 
Put these words on the back of your bedroom door: Did I back up my ---steaming pile of meadow muffin--- today?
+1. I always backed up my files. Until the one time I didnt and lost my wedding photos. Luckily my wife had all the digital copies on facebook. It doesnt hurt to buy a cheaper hard drive with the same amount of space of your files. Or invest in a WD passport type device and partition for all your computers. You can always reinstall an OS or program but certain files like pics, music, videos not so much.
Its funny you bring this up Eric. On a semi related topic I put in a bunch of information into a spreadsheet over the course of the day today. It took about ten hours working on and off on it. One of the guys who had access to it saved over all of my work and now I have to go back in about 5 minutes and rework the damn thing. And Im the one who will look like an idiot because he saved over it. Point I am making is assume nothing you create on a computer is safe.