I've had severe chronic fatigue syndrome/myalgic encephelopathy for the last eight years and took on betta keeping (with some apprehension, though I love bettas) in the hope that I would be able to redirect my focus, I also felt ready to take on the responsibility and thought bettas were the right choice. There was the added bonus of gradually working up my physical strength through water changes etc. I have my mother on-hand if I'm having a "bad day" and she is more than willing to help me with water changes should I struggle, I will always be grateful to her for her support.
So far I've not done too badly, I've had days where I've thought it would be wisest to rehome the fish but at the same time just sitting and watching them is more than enough to reassure me that I can take care of them... and I have been! It's so wonderful watching something you chose to bring into your home and your heart thrive under your care. They never judge you, they never shout at you if you find you can't brush your teeth or wash your hair, they don't honestly care about all the trauma, frustration and pain you feel -- they're just there to brighten your day and you're there to brighten theirs (even if it's just because you feed them!). I don't know of many greater joys (whether due to under exposure to the world or because I find joy in the simpler things) than pouring your heart and soul into an animal enclosure and watching its inhabitants (both flora and fauna) burst into life and thank you through their bright colours, vivid personalities and hilarious antics!
Of course I wouldn't recommend fishkeeping nor other animal/plant keeping to everyone who has an unfortunate circumstance, but I don't feel that people should be disallowed to care for these animals because of circumstance either. It's purely down to the individual to decide whether they are ready to handle all aspects of animal/plant keeping (mental and physical) and it is down to them to follow through with that responsibility.
I often find that when my heart has chosen something my body follows. Sure, I sometimes suffer the consequences and end up in immense amounts of pain but in all honesty that is all worth it when I look at the aquarium at the end of my bed and see those little fish dancing around and flaring at random bubbles. I make sure they're fed, they're warm, they're occupied and they're kept clean. That's all I can do for them but it sure feels good!