I also have a real box (my T called it a 'containment' box) where I can put the things I can't deal with on paper and close the lid on them until it's time to deal safely with them. I put a picture from a magazine on my box. The picture is of a bank vault door closing. That imagery really helps me to understand what the box is all about. The door is open just a crack so I can retrieve issues when it is safe. You might want to talk to your T about using a real box - it doesn't have to be very big, just big enough to hold a few slips of paper. I find that writing down the troubling thoughts to be helpful. I think your T is on to something here. Good luck.