This is really nice, very calming. I will admit, I feel like the intro lasted a bit too long since single notes on the piano don't offer so much, but that prolonging made the entrance of the strings that much nicer. I really liked at 1:28 when the melody is brought up into the higher register, it sounds quite nice. All in all, it's a nice and pretty peace, but I do agree with Fataliante's comment regarding giving the piano more personality. There's nothing wrong with doubling the melody, but for the whole piece is questionable. Right now if you took the piano/violin away, the tambre of it would be gone, but everything would still be there in notation wise. The song would still really be the song, but with one less instrument. If you add harmonies, a lead, or a counter melody and then take those away, you'd be taking away much more than just an extra instrument. They're two separate entities, so treat them as such and let them stray from eachother.
Overall it's an enjoyable piece, good work