Very short and sweet. I am no professional, so I won't go in too deep about this piece. However, I do feel like it could have been... breathed into a bit more. When using short, choppy lines, it does matter a great deal more what words you choose to use. For example,
"It's cold here
Could easily be changed to something along the lines of
"It's frosty here
Although, you would know better which words would describe your feelings more so than I.
My favorite part was:
"Its been so long here,
but I can't say
that I've missed you."