I'm exactly like this too. I hold back the tears even in therapy and most likely somewhere along the line, I've managed to block out the trauma of the memories. So instead of a "normal" expected reaction I flippantly discuss these things with gallows humour. For me, the act of kicking off my shoes and bringing my feet up onto the chair is the insurmountable barrier. I'm sure that if I get over that first bit I wouldn't have a problem with hugging my knees and rocking back and forth.