Moreover, storing Git repositories on the same storage device as your
original files only safeguards your data against your own mistakes. This
is analogous to the (opposite) misconception that RAID systems serve as
a backup solution; they only protect against hardware failures of one or
more disks, and happily mirror all your mistakes for you. Proper backup
system need to protect your data from most (ideally all) data loss
scenarios.
Fortunately, with Git, setting up remote copies on another disk or
machine is straightforward, so it is an excellent backup tool for data
sets that are well suited to version control, such as your writing
projects.