As Ben said, so much imagery here. The emotional contrast of inner heat/anger presented on a calm/reserved/cold exterior came to mind. There are some people that have these inner cores that they hide, for fear of showing themselves in a less favourable light. There are perceptive people, usually someone close, someone open of heart, who can see through this mask, see the truth that lies within. But there's a cost, isn't there?
There is a ton to like about this poem. I'll get the technical stuff out of the way first. I love how the punctuation is placed, it gives each line room to breath and it makes sense because this is such an emotional poem. I wouldn't personally change anything in that sense.
The imagery is well done but not over done. I also love how you worded this poem as well, because on the surface This might seem like a hopeful poem, but in reality and in the title it is not. Your perspective of PTSD is wonderfully sad and yet relate able to many persons. This persons face burns within you from years and years of hurt.
Because of the hurt you have become winter like or cold to anyone. No one but you has seen this person for who they are. That often happens when you go through abuse or just some kind of hurt.
I loved the story told and the perspective of each line you have written.