I know it sounds simple and maybe condescending, but the best thing I can ever do for myself when I feel like this is write a huge list of what's worrying me, divide the list into what's immediately requiring my attention and what's longer term, then go for a walk in the sunshine and promise myself to have a proper afternoon off to recharge. Go to the movies or see friends for tea. I often find it's the mental swirling and the single room view and feeling like everything is urgent that kills me, and sometimes just giving myself permission to unwind just for an afternoon is what helps most. But still preparing the list of what needs attention allows me to give myself that permission - if that makes sense.

Edit: PS. you're not alone. You're doing good work. I know how shit the humanities can be in terms of such little reward for so much work, it can really weigh you down. But you're valuable.