I haven't had all the sickness/disease you have had to deal with, but I am right there with you on wanting to just sell it all and get out of the hobby at time. I started a thread a couple days ago about being "burnt out". Didn't get many hits, but I understand where you are coming from.
In the end a hobby has got to provide enjoyment. All hobbies can come with challenges, and that is good. Hobbies are often meant to help us extend and progress as much as provide enjoyment. That said, it is essential that there is enjoyment.
In my psychology classes I learned that the recommendation is 20 min of personal enjoyment and 20 minutes of exercise EVERY DAY! Both provide endorphins that boost our mood, but it takes our bodies about 15 minutes to produce them and then you need a minimum of 5 minutes to have them do you any good. If you are not getting any enjoyment out of the fish, and just adding stress to yourself...it can be rather destructive.
I feel like am being a little long winded, but don't hang on to something you don't enjoy. If you can make changes that will help you enjoy it again then do it. Other wise, its a good thing to move on. You could be holding yourself back from something that will provide the enjoyment you need.