This is a mantra that is constantly being chanted on the forums, but people are still not doing it. This include me. I've just caught my foot in the power cable to my notebook (I'm in KFC at the moment).and the computer crashed down onto the floor as it was loading a thread from Bitcoin Talk. I'm by a window, and it hit the lower frame just above floor level. Panic set in, as I must be about 3 months behind with my backups. Fortunately, apart from a small chip out of the plastic lid casing, it doesn't appear to have done any damage.
I bought a 2Tb backup drive some rime ago, but it isn't any good if you don't use it. It's so easy to copy your data, including the blockchain and your wallet, so do it regularly. You may not be as lucky as I was. There are other problems as well. Your computer could be stolen, or you could spill coffee or worse over it. and I haven't even mentioned mechanical or software failure.
And this is why i love desktop computers. So heavy you can't take them out and therefore unlikely to fall and break apart, or be stolen. I think a portable should always be considered a secondary device, never primary.
As for backups, just copy the data you create yourself. Don't bother with programs or things that can be downloaded or bought. It would be better if the backup was stored encrypted, but lets leave that for another day.
You would be surprised how old this "mantra" is. I think its as old as computers, especially when personal computers started appearing in the late 70ies. While media and methods have changed a bit, the recommendation remains the same.
This time you were lucky. Are you willing to tempt the odds again? Oh, external hard drives (with spinning discs inside) don't like getting hit, even falling from vertical position into horizontal may damage them, and i clearly remember a 2" Samsung external dying after falling from a table. Once again, things are so safe inside a sturdy desktop or server computer case...
