There hasn't been a complaint (yet), but apparently I do the 'aggressive' thing to quite a few co-workers, clients and other people.

The problem is that whenever something changes, or I'm asked to do something that I wasn't expecting to be, I get anxious. And, when I'm anxious, I apparently appear to get aggressive or intimidating. I'm over 6"3, and pretty bulky, so I imagine that my size is a significant factor to this. I'm pretty sure that the 'aggressive' or 'intimidating' look is really just me being defensive, unsure or anxious, but I need to find a balance.

I was thinking about some type of professional development course or something, and the idea of drama classes might work. I've worked pretty hard on my behaviour in the past, and thought that I had it under control. HR wouldn't suggest it unless it was seen to be an issue.