My computer hadn't been behaving at all strangely. Oh, it had hung a few times while I was browsing the Internet, but that seemed to be my browser, not my hard drive, and each time it recovered. Otherwise it was running great, just like usual.
Until it wasn't, that is.
I went to turn it on the next day, intending to work on a project whose deadline was looming, and it just wouldn't boot up. No warning or anything -- the night before, it had shut down just like normal. As the realization sunk in that no matter how many times I tried again, it wasn't going to work, I wanted to cry, scream, throw the computer through a window -- anything to express my frustration at all the important data I'd lost. How long had backing up our tax files, my work files, etc. been on my to-do list? For how many weeks had I put it off "one more day"?
I lucked out. When we took the computer to a repair shop the next day, it turned out that I could still access the data -- the computer just couldn't boot off the hard drive. It was all still there; I didn't lose anything.
As I said, I lucked out.
The hard drive was toast, so I opted to replace it rather than getting a new computer. In the meantime, I moved the files I needed most to a flash drive and an external hard drive, and brought it home to work from my old laptop, which I'd thankfully kept as a backup.
Hopefully I've learned my lesson from this near catastrophe. I'm planning on keeping my backup flash drive on my desk or hanging from my bulletin board -- in plain sight, so that I can get back into my old habit of backing up at the end of every single day. I'll (hopefully) never again shut my computer down without backing up, just in case it doesn't start up again the next day.
Don't let yourself get caught in the same situation. Learn from my mistakes and back up your data today!