One of your better pieces. The face is alright, looks decently stylized but everything else is garbage. You try to go for a pseudo-realistic face then make everything else look like lazy grade school 2-d cartoons.
Rivers are not one-dimensional in cover. Grass is not one dimensional in color. Shading is a thing. You rely on bright colors too much in this piece, not enough contrast.
The horse is okay, believe it or not. Legs need work though.
Don't even get me started on the mountain and sky. Have you ever fucking been outdoors? It doesn't look like this shit.