On the left here is your original and on the right is my remake of it.
The major difference would be that I softened the outline, but kept it so that it wasn't too dark. I added highlights on the border where necessary to give it a metallic shine, but I never brought the inner highlights close to the edge so that it didn't contrast a lot and give a rigid look. I hope this helps.

(The reason it may still look rigid is that it's a small image and AA doesn't really help on edges like that. I hope it helped you somewhat though.)