I'm sad that it is over, but I am happy it went out the way it did.
Same. I was low-key bummed out after watching the final season, for like two days. I don't remember when this last happened for me with any piece of fiction.
Since distracting myself didn't seem to help much, I finally I gave in and rewatched first the final episode, and then the entire series from the beginning (which I recommend, because some revelations and character development actually make the first seasons better with the benefit of hindsight, and colour certain interactions completely differently).
On top of that, I'm seriously considering writing, like, an article on Medium or making a video on Youtube with my thoughts on Catra's character and arc. I don't think I ever had a strong impulse to do anything like that (even though I'll probably end up not doing that, since I'm neither articulate or insightful enough).
Bottom line: the show impacted me in a way I had not anticipated, more than even shows I theoretically think are even better.