My T use to say I was like a stuck thermostat, had no emotional regulation; everything was equal ("A wet towel on the bed is not a murder" -- was to me :-) and maybe you have some of that if you get angrier discussing what is making you angry. Presumably you are not angry about something in therapy, "words" aren't that angry-making on their own so you are probably thinking about and discussing something that happened before, in the past and thinking about it makes it present again? Does sound like you could use some help differentiating between what is happening in the present and your thoughts, memories, and feelings about something that happened before.