i like the phrase open shadow and i like the main part "on a day you were unhappy..." i find it interesting that the person was unhappy during a sunny day, which most poems it seems has people saddened during gloom or darkness.
"trying to fight darkness without touching it." this one is my fave line, i think it's verry fitting.

I liked that. The connection with shadows and doors worked extremely well as a metaphor.
Good work. And thanks for the review.