Holy crap. This is so beautiful. That last face is everything. Composition, color, storytelling, mood, all chef's kiss. Since you asked for constructive criticism, one nitpick is that your horse anatomy could use a bit of work. It stands out to me as a big horse nerd hehe. You probably just don't draw horses much, since clearly you don't struggle with human anatomy AT ALL. That face, and that eye animation are just gorgeous. Super high level of skill.
