first he gives up snog resistance and lets me kiss him all over his muzzle as much as I want without trying to break my face, then he starts cantering towards me instead of jogging around the field laughing at me when I go to get him, and now when I turn him out he doesn't roll, find his friends, graze but falls asleep with his twenty stone head resting on me. 
Is he dying? He seems lively enough under saddle. Or is my great love for him finally requited? Or has he been up to no good? What does it mean?