First, it’s important to note that this answer applies only to traditional mechanical hard drives and not to solid state drives. Never perform a defragmentation operation an SSD as doing so not only provides no performance benefit, but it will also add excessive wear to the drive’s limited lifespan.
Two main points to take away from his article: (1) Never defray a SSD, and (2) Defrag a traditional spinning drive about once a year
Oh....and backup your data before defragging it. Any time you start moving 1's and 0's around you have the potential to lose those 1's and 0's.