Space is cheap. Text is small.
Make a folder for every project.
Make another folder inside and name it after the current date. Keep the files inside by whatever order you want them to be. If they're individual chapters, putting the chapter number first would be useful, but mostly, use descriptive file names. We're not in DOS times anymore, file names can be very long if necessary.
The next day, make a copy of that folder and rename it to the new date.
That way, you'll have a complete daily history of all changes you make without a lot of effort. You can get a flash drive with a couple of gigs for a few bucks, so get two, and make a backup copy every week or so, alternating them. A flash drive will hold a couple of billion pages of text, so even a big project and daily backups mean you only need to worry about deleting old backup copies every few decades or so. If you want to be paranoid, keep one of the drives with your computer and one on your person.