The big SSD downside is that it has limited write cycles. So, anything that needlessly uses that quota, is an absolute no. Let’s list some:

Using SSD with small RAM quantities
If you are that kind of person that keeps a lot of open browser tabs, apps running in the background, photo editing, video editing, virtual machines, your system will use your SSD to keep your apps from crashing when RAM is full. So, it takes a portion of RAM and writes it completely to your disk. As you keep changing apps, your OS will keep swapping memory pages, writing again and again on your SSD, thus reducing its lifespan.

Keeping your SSD full
Modern SSDs have a wear leveling feature that usually increases its lifespan. It does that by moving some data around and keeping a record of which cell has been mostly written to. As it moves files, it needs empty cells to act as a cache. If you have little to no spare room, those same cells will be used over and over and it will fail sooner than expected.

Defragmenting

We needed to defragment those old spinning drives, as data was usually written all over the place. Defragmenting it would make sure that correlated data stayed together (on the same ‘sector’), reducing the read time. On SSDs, this is absolutely not a problem. All data can be accessed right away, no need to wait for the plate to spin again to reach the next second of the song that you are listening to. So, gathering data together will simply waste those write cycles, with no increase in performance.