What keeps me coming back? I love the fish, the corals, making the rocks, designing and printing new little toys for the tank, etc. Speaking from the place of having had 3 tank crashes or full resets over the past 20 years or so, I find that, while there are some annoyances and challenges that aren't fun at the time, the successes almost always seem to outweigh the lows of the hobby.
I've been frustrated when my first tank lost every fish and coral with the exception of hairy mushrooms and then was overrun with GHA. I was in the process of moving and, unfortunately, wasn't able to devote the necessary time my tank needed.
My second tank was a success a few years later, but it was a 5 gallon Pico.
My third tank was thriving - until it wasn't. A magnet inside a glass scraper started rusting and began leaching into the tank. GHA quickly overtook a lot of my corals. Once I found and removed the magnet the GHA slowly started to retreat. However, the Montipora in my tank were really struggling still. That's when I noticed the Montipora Eating Nudibranches at the base of one of my Montipora. I was able to get rid of them through perseverance and patience but not before losing several hundred dollars in Montipora.
My fourth tank was doing good for a couple of years. Unfortunately I received a coral frag that had a hidden Aiptasia. That single quickly became many. Soon, my tank was an Aiptasia farm more than a coral display. Berghia eventually wiped out the Aiptasia but I waited and let it get bad so it took a long time to be successful.
My current tank has gone through Dinos, GHA, some Aiptasia, etc. I've learned over the years to be patient and persistent and work at the problems/concerns while their small and not to just "throw" solutions at them and hope something sticks.