Many cyber-hugs to you mears - and many cyber-non-hugs to your manager!
I know what you mean about 'choosing' how to respond to certain things - very difficult to explain isn't it!!! I had a horrible work situation a few years ago and had occupational counselling which was really helpful. I found a really key thing for me was the 'choosing' thing - it made me feel that I had some kind of control over the situation (ie try as they might to provoke me to guilt, anger, stress etc) I choose not to react in that way. In order to be able to do that though you are right, it does require insight and that can be very difficult to find in the heat of the moment!
I also found it quite challenging about how honest you have to be about your feelings to do the 'choosing'. Stupid example now, but recently I found myself saying that HVs had made me feel guilty about giving DS jars of babyfood. Now, the HVs may have been trying to make me feel guilty, but the actual feeling guilty was down to me and my own issues - still not sure that I've expressed it that well, but I wanted to let you know that I know what you were trying to say and that I agree with you!
I found it really difficult to remain calm and confident in confrontational and difficult situations at work, and felt inadequate for being unable to do so - however what worked really well for me was pretending to be calm and confident - I acted out a calm and confident role whenever I was in that situation, and it really helped. Even if I was panicking and stressed out in my head I made myself come across as calm, and by doing this it makes sure that you keep breathing regularly which, in turn, helps with staying calm (wish I could have done that in labour!!).
Probably raised your stress levels just by having to try and work out what I'm trying to say - maybe I just should have advised a glass of wine and Saturday night T.V!
I hope things become less stressful at work - it makes me cross to think of anyone not appreciating you!!