I'm so sorry for your circumstances. I guess it's because life is a complete crapshoot. You may not have got tinnitus or covid. It's just luck- or rather- bad luck a lot of the time.
I guess we try to give ourselves the best chances in life we can. That often does include working hard to learn something. Working hard on maintaining relationships. Keeping fit. All that. If we didn't even bother with all that- our life would take a different route. Maybe it would turn out better but, maybe not.
I think most people pursue things and work hard because they have ambition. If you have ambition to become a surgeon or a musician or a pilot- you might not feel too happy quiting your education to work in a shop. Not that there's anything wrong with working in a shop but- if you don't want to be there, it can feel like hell. So- we do our best to achieve the things that feel important to us.
I can sympathise though. I have more sympathy for you than me. My failure isn't due to ill health. Still, I worked hard and made sacrifices in life too. I gave everything to my creative job but- my job isn't financially stable. I commited all that time and spent all that money and really- I'm quite probably in a worse place trying to get a wage slave job now than a school leaver. Sometimes, it does make me wonder if it was all worth it but honestly- if I hadn't even tried, I'd likely be just as unhappy now. We have to try to find out I think.