How to answer this dreaded interview question?

Okay I have a couple interviews coming up. I don't know how to word an answer to why you left your last job?

At this particular last job they did let me go BUT when I asked why they were doing so they wouldn't give a reason. But, I have a suspicion it was due because I was finally demanding I get my day off back so I can go to all the appointments doctor/eye doctor/dentist/ I suffer from migraine s that I am trying to get handled so neurologist appointments. We lost our part time person , the other tech and I started having to work our days off so I had to work Mondays she had to work Fridays. But, we hired an assistant to help on fridays but not Mondays so she got her fridays back off. But before this even happened with COVID I rescheduled a lot of my appointments because we were constantly short staffed and I was now catching up. I mean I literally was trying to get my migraines, a root canal and cavities filled, hadn't had my eyes checked in two years etc. SO about 3 months into me still working Mondays and the other tech got her fridays back off I went up to my boss and said I have appointments scheduled on Mondays because those were my days off I need to go to them she said it was fine. I offered to come in before and and after she told me no because you deserve to have your Mondays off. I mean I was always the first one in setting up for the day and staying late while the other tech came in sometimes an hour late and left early. I never stopped working while the other tech was on her cell phone etc but I got let go it seems because I finally was taking care of myself ON MY DAY OFF.

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But like how do you answer the question why did you leave? If you weren't given a reason and really I don't want to sound like I am bashing them but it was a horrible workplace and I was actually planning on leaving anyway. They didn't offer health insurance. And the head tech wouldn't let me do surgery which was hindering me because I told them I needed more training in that area when I started and she would literally kick me out and the doctor/owner wouldn't only want her for surgery. When I
How to answer this dreaded interview question?
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