I am sooooo angry with my son.
I think the basic problem is that I haven't forgiven him for some 'big' stuff (stealing from me; kicking off so violently I had to call the police) and so I have a backlog. Sometimes I feel I'm like a pressure cooker on full heat, and little things will make me boil over. And then, some of his 'little things' don't feel little to me at all, and there's always more to deal with, just as I 'resolve' the last lot of crap. So for example, last night he didn't come home as agreed, woke me at 1:45 to let him in, spent the car journey to college this morning arguing about why that was OK, called me a 'moany sh*t', and walked out of college after I'd spent an hour getting him there. 
I don't think I shout much, tho' he doesn't agree. I do tell him what I don't like, so I'm a nag (and a 'moany sh*t'). Sanctions are problematic because he can almost always 'trump' me (e.g. not coming home last night was 'revenge' for me telling him off for taking two beers without asking... And if I refuse a lift, he doesn't go to college, etc...). I do have friends I can offload to, but sometimes venting just isn't enough...
I have got my GP to refer me for counselling, but meanwhile, does anyone have any practical tips for dealing with this kind of anger and frustration?
I'm not looking for advice on what to do about him (I have another thread on the go about that, and anyway, I've more-or-less come to terms with the fact that I can't change him) but I do need some practical strategies for how I can deal with my own emotions, and particularly how I can disengage a bit and stop him 'getting to me', or I'll get ill.