I'm just going to reiterate
I have to agree with a lot of what other people have said. Like darkriku12 I think dynamics would have been a helpful tool. Everything seems to be at one level the entire time. I think the few slow downs that there were helped a little bit but overall it feels mechanical and almost soulless. That's what gives the most sadness out of anything.
A few tweaks to the dynamics would really show a lot of change. Decrescendos or crescendos will work almost anywhere in piano solos as it is a dynamic way of filtering dynamics. I wrote a song called Silent Nights and I added dynamics to the beginning only and they are very noticable if you listen to them. It will do a great deal of change to the song. I did notice a few here and there, so I'll give you credit on it. I think this song has potential for improvement.
Overall I thought it was a very beautiful piece that does capture the emotions of sadness and sorrow.