When I started out, things were much easier. The only computers were mainframes, and the only word processors were Wangs. So almost every author either wrote by longhand, or typed, and all backups were in the form of atoms. I typed my first stories and my first published novel, backing up first with carbon paper copies, and later on by submitting photocopies. I graduated to bit storage with my first computer, which used 5.25" disks. Later media included Zip disks, and 3.5" disks, which as well as accumulating new files were also imprinted with copies of old files that travelled from computer to computer. And because files produced by old word-processing programmes aren't always compatible with new WP programmes, all final versions are saved in WP and the universal .rtf format.
But even bits can rot. As I prepared to copy-edit old WordPerfect 5.0 versions of the first two Confluence books, I discovered that chunks were missing from the files thanks to some copying error that must have originated in the WP program - all back up files were identical. Luckily, copies on atoms saved the day. I spend several evenings over Christmas razoring out the relevant pages from the relevant US hardbacks, turning them into text files using my scanner, correcting the (surpriusingly few) errors in the resultant files, and patching them into the existing WP files. If there's a lesson in all this it's this: keep backup copies of everything. Including your own books.