Full sympathies, Steve.
I started seeing a psychologist a few weeks ago due to feeling overwhelmed from attempting to juggle so many things in so little time -- with my final law exam looming in three months' -- and struggling with feelings of anger and frustration (and guilt for those feelings!)
The main point that came out of my first few sessions in relation to my work stress was the need to identify what are your responsibilities, and what are others' responsibilities? Are you taking on stuff that really isn't your 'problem'? (whether voluntarily or by not successfully resisting when others push it onto you)
If (a) you weren't hired to do it, (b) you're not being paid (extra) to do it, and/or (c) you've not been promoted (so that it
is now your responsibility when before it wasn't, with commensurate payrise let's not forget!) --- then....
.... it's not your problem. If there's too much work, that's your employers' responsibility to sort out e.g. hire and train more people, the
right people.
This was never a situation of
your making. You did your best, but it was not your responsibility to become the solution to what are essentially your employers' staffing and management failures.
Enjoy your break!