Overwhelmed,
Im not a doctor but it sounds like your anxiety has become depression. Do you see a therapist or have tried any mild anti anxiety medications? I know the feelings you have, the anxiety and lack of personal purpose become overwhelming. It feels like we are trapped and cant make any plans as our lives are on hold intil these adult children grow up. The fact that you live your job and your children, tells me you havent been able to cultivate any other interests for yourself alone. This is not valuing ourselves. if we don’t value ourselves how can we expect anyone else to. I also work and let my difficult ones overwhelm me but I also go to a seniors aerobics class twice a week, i joined a bike riding group in the summer and I belong to a ski group in the winter. These outside contacts are so important to me, I give them priority when I schedule my days. For many it is church. I also had a therapist for a time, was the best thing i ever did for myself!! Even going for a walk every day is wonderful. pick one small thing you’ve always thought of doing for yourself thats easy to accomplish, maybe something you can do on these days off rather than staying on the chair and getting more depressed. and then make yourself do it, at first it’s difficult to get the motivation but eventually it can become a habit, after a while it seems to take on a life of its own and it becomes as important to prioritize as your job and your children are. and guess what you’ve then started to make your self a priority, you’ve started to value yourself more and it is a real psychological change. once you learn to value yourself it becomes easier to say no to others. Im Definitely a work in progress still, But I feel I’m moving in the right direction. there was a time that my needs were the absolute bottom of the list so needless to say they were at the bottom of everyone’s list . If you can’t get that motivation no matter what, it may be a therapist is the thing you need to do for yourself. anxiety can very easily become depression and once it does it is so hard to get out of that funk. It makes mountains out of mole hills and it controls us physically and emotionally. Good luck and I hope you feel better soon
and Love 
