I've learned this lesson about 20 years ago, when the 250MB hard disk of my 80486DX2 failed. I had no backups, except for the latest few files I needed for school. I lost many save games and thus, tens, maybe hundreds of hours of progress that day
In my defense, back then making backups was very expensive, requiring either a second drive in a caddy, or a tape streamer. Or, 200 floppies....