Now that I have OS X Mountain Lion on my Mac I've switched to the Pages app, which saves documents to the cloud (bonus: I can work across my devices without e-mailing them around).
I also have a Time Machine to back up all my files, and when I make significant progress I'll e-mail the document to myself so it's in Gmail's cloud too (just in case something happens with Apple's cloud and my apartment is struck by a meteor).
Paranoid? I say careful!
What about you? What's your method for making sure you don't lose anything?
Art: Woken-Studie by John Constable