Facebook has a simple process set up to create a zipped file backing up your videos, photos, and text that you've uploaded over the years.
1. Go to settings (using the drop down menu by clicking on the "settings" arrow noted in the picture below).
2. Choose "Settings" > "General" > "Download a copy" (noted in the picture above).
3. Then just follow the directions, including waiting for an e-mail and clicking the link to archive.
Be aware that the archive downloads as a large zipped file, so don't unzip unless you have enough memory. It's not a perfect backup system, but if you are ever without Facebook, it's something.