that brief moment of horror when you realized you deleted what you thought were copies of several important files but were actually the only instance due to you just moving them instead of copying
followed by intense relief when you remember that not only are your files automatically backed up every hour or so, but that you explicitly told Time Machine to make sure your backups were up to date before making that mistake
I’ve said it before, and I’ll say it again. If you’ve got a Mac then get a big external drive, plug it in, and tell the system to use it for Time Machine. If you hate plugging stuff into your laptop then get a Time Capsule. If you’ve got a Windows box then… um… does Windows have built-in backup yet? I hope so. Because at some point you will make some stupid little mistake that wipes out a ton of hard work, and be delighted that you can recover in seconds.
And then sign up for a cloud backup service, so that if theft/fire/etc happens to your computer and the external drive, you’re only out the cost of a new machine, and not all the stuff on it.