I know exactly what you're experiencing - I'm going through very much the same thing myself at the moment, mostly work-based also..
The most useful thing I'm finding is kokyu-dosa (breathing technique), though I've been extending this further to a form of meditation based on 'mindfulness' of your breathing.. Essentially it comes down to only focussing on your breathing, in, out, calmly..
If other thoughts intrude, don't try and quosh them, just let them fade away on their own (otherwise it can be like someone saying 'Don't think of the Atlantic Ocean..!'
I'm also finding that helping out with the Junior's class helps, it gives you an external focus, so you don't have time to do any
dwelling on problems!
If you do find anything else useful, let me know!!