Title says it all. The longer you stay at a job that degrades your mental health, the more damage is done to your mind, the harder and more expensive getting back to a healthy mental state will be.
Work culture will have you believe that your mental health is elastic. That the few hours after your shift is over and the few days you get off is enough for you to regroup your mental health to take on more mental anguish in the following week, and that's just not true.
Start thinking of your mental health as you would your physical health. If a job requires you to physically break your back daily, the weekends will never be enough for you to recover. Eventually, that constant back-breaking pain will destroy you. Eventually, you won't be able to work in the back breaking job anymore if your back is completely destroyed.
The same goes for mental health. If you stay in a job that destroys your mental health daily, then eventually, you will burn out and you won't be able to work in that position anymore. Your vacations will eventually turn into an expensive week of worrying about your job and your mental health. Life will lose its color and it will take a toll on your family and relationships.. Take care of your mental health as you would your physical health so that you can live your life the best you can. If a job is taking more than you can give mentally, it's time to find a new one.
Take the leap. Leave the job that's destroying you in anyway you can. Make an 'escape plan' if money is tight. You can do this. I believe in you.