Day 48: December 9 - Tired?

Today Poncho went back to being a lot shorter. He wouldn't maintain a lope for long, and he wasn't very willing to keep trotting laps either. I tried switching things up with going over the jump and whatnot, but it didn't really seem to help. But, at the same time he didn't act like he was being dominant. He wasn't breathing hard, and we didn't do too much, so I know he wasn't just needing a break. Is it possible for a horse to just be tired? I know that as humans, sometimes we just don't get enough sleep, so we're tired the next day. That's kind of what Poncho was acting like, but I just don't know if that's really even possible for horses...