When was the last time you backed up your work?
There is nothing worse than finally getting down that perfect scene... or chapter... or novel... only to have it be devoured by a nefarious computer monster.
I save my work on an external hard-drive, and I also use Dropbox, which is is a file sync/backup service that automatically saves your files to some sort of magical internet cloud, from whence you can later retrieve it using ANY computer (once you've downloaded Dropbox onto it). In other words, if I'm working on my laptop and I save my WIP to my Dropbox folder, I can open it on my friend's computer when I go to meet her at the coffee shop down the street.
Or, perhaps more importantly, I can open it on my NEW laptop when the hard drive on my old one is eaten by the aforementioned nefarious computer monster.
Ah, technology, you are at once so terrible and so glorious.