In the GeneaBloggers Community, the first day of every month is Data Backup Day.
For most of my backup needs, I rely on my Mac's Time Machine software, installed on an external hard drive. The software takes care of itself, every hour making an incremental backup of any and all changes, allowing me to go back in time an hour, day, week or month to see what my computer looked like then.
But there is still the slim possibility that my computer and external hard drive could be destroyed simultaneously. (A fire? I live in St. Louis, and know that it was a fire here in town that destroyed most of the 1890 census records.)
I store copies of several important files "in the cloud" using both Dropbox and Google Drive. I also have more than one Google Gmail account, and have mailed important documents to myself, storing copies in both email accounts.
Whatever means you use, it is important to have a plan, because otherwise it is too easy for important data to be lost in a computer crash.
[The image is a modified version of Winslow Homer's Blackboard (1877)]