My partner did it a couple of years ago. He started a new job which was awful. Nobody trained him but he got reprimanded for not knowing the processes, there was no new starter induction and he wasn’t introduced to anyone. He was expected to pick it up as he went along, and figure it out himself. The staff were openly rude about their colleagues and rolled their eyes when mistakes were made.
He became very stressed, thinking he was just not up to scratch and failing. He became distant and couldn’t sleep worrying about the next day, Sundays were always spent dreading about starting a new week. Eventually after he got a loud telling off from a manager over something minor he walked out at lunchtime. He went straight to his GP who took one look at him and signed him off as he was so visibly stressed.
It was like a weight lifted. He handed in his notice and started looking for something else immediately. It was like he returned to himself overnight. In the end he was out of work for about 2 months, but we had a savings buffer and he lived very cheaply (no commuting costs, simple lunches at home, skipping expensive nights out) so financially it was fine for us.
I think it’s always best to have a job to go to, but if your current role is affecting your health and you can afford to be out of work for a short while then it’s OK. Although I’m not sure how long we could’ve sustained it if he had been out for longer.