Though it's always important to keep looking forward - not constantly looking back - backing up is a very good thing to do. And I do mean "backing up" in more than one way...
As a photographer, writer, or whatever you are, it's very nice to look back upon what you've done, and to see how far you've now come. It's also nice for remembering tricks, information, or techniques you may have forgotten about that are extremely helpful.
Backing up your information is even more important though.
No matter how solid your computer is, no matter how confident you are that it will never crash... ALWAYS back up your data! Whether that be to a portable hard drive, or just backing up on CDs or DVDs, I cannot express enough how important it is to back up your data.
PC's, MAC's - no computer is exempt from something awful happening to it. Trust me, I've had a hard drive go out in one of each.