I love the concept of the emote creating the heart. It is sweet and thought out well. I have a few things to point out though that could use some work.
From my experience it's best to keep an animation short or, if it is long, have it at a faster pace. Nine hundred frames are quite a lot. Maybe it could have been broken down by having the emote pick up larger pieces of the heart. Also the movement of the emote is slightly on the slow side in the beginning. If you play around and delete possibly every other frame, it would speed up but you'd have to be careful because to much movement from frame to frame will look choppy.
Transitions are amazingly useful. It is so interesting how one or two frames can make such a difference. If you added a cross faded frame from the (RED) to the actual heart, it would look so much better to the viewer. When I say cross faded, I'm talking about a frame that has say 50% opacity of the (RED) frame and has 50% opacity of the heart frame overlapped and added as a single frame between the actual (RED) frame and the heart frame. I hope that makes sense because I'm not very good at explaining things.. Also if using 50% is too choppy, then try advancing it by using three extra frames instead. First frame would be 75% (RED) and 25% heart. Second would be 50% (RED) and 50% heart. Third frame would be 25% (RED) and 75% heart. If you tinker with it then you'll know what works and what doesn't.
That method I just explained could also be used on the emote itself when it changes colour. The sharpness and instance of colour change seemed odd and out of place when I viewed it but if you transition the colour, then it will become more appealing to the eye.
Overall there is a lot of room for improvement but it is a good starting point to build on and learn from! You also did a good job with what little time you had. Like I said, the concept is really nice and I think a lot of deviations lack concept so there is always something good to be said when it is present.
Also from my experience, there is always a bit of let down when you've worked on something so diligently for so long with hardly any recognition and especially if you enter a contest and lose. All I have to say about that is winning is not everything and, like I've previously said, practice will make you better and each deviation will be a step in the right direction if you work at it. Good luck in the contest by the way. c:
Keep at it! C: