I have a tough time with this too. I often do 11 hour shifts in an active job that also involves listening to other peoples problems/pains and helping to get through them. I know it's not easy and really feel for you!
I found writing a list of the things that I enjoy doing and make me happy, really helpful. I keep it in my purse and a copy on my bedroom mirror and it reminds me to do those things!
Its just simple things like reading a book, listening to music, going for a walk, painting my nails or having a bath. Even when I don't have much time and there are things that I should
do, I try to stop and as myself...."what do I need to do?"
If I know the housework needs doing but I am grouchy and will only stomp about and feel the pain that it causes so much more, I put it off for between 10 minutes and half an hour and do something from my list first. I often find that 10 minutes is all I needed to make myself feel better then I get down to the things I should do. Usually in a much better mood and in the case of the housework, with my favourite music blasting!
Things don't get done as fast and often aren't finished or perfect but my partner is very supportive and would rather have a little more to do himself than have me miserable and snapping all of the time! I know you'll probably feel guilty at first (I still do), but I really have found that It's better for my life and relationships in general if I look after myself....even if its just for 10 mins a day!
As for work....do you get a break? If so get out!!! Even just getting out of the building that I work in helps me to relax and switch off for a while. If I can't I find a quiet corner out of the way with either a book or my ipod (not the staff room as it's always busy and noisy!).
Of course all of this may be rubbish to you, as it's just what works for me but I hope it's given you at least some ideas!