How do I structure a productive solo practice session between working cow horse lessons?

A productive solo practice session between working cow horse lessons is built around specific targets rather than general riding, and the most useful starting point is the homework your instructor assigned at the end of the last lesson. Before mounting, write down the two or three specific things you are working on — the exact exercise, the quality standard you are aiming for, and the correction you were told to make — so the session has a defined purpose that you can measure against when you finish. Begin every session with a warm-up that assesses the horse's physical and mental state that day, because a horse that is tighter or fresher than usual needs the early portion of the session addressed to that reality before any specific homework can be productive. Work the reining elements of your homework first while the horse is fresh and your own focus is sharpest — stops, spins, circles, lead changes — and address the specific quality corrections your instructor identified rather than simply running through the exercises without attention to the particular details that were flagged. If cattle work is part of your homework and you have access to cattle, keep the cattle session brief and focused on the specific skill being developed rather than doing full cattle work sessions that exceed the targeted practice purpose. End each session when you have produced a clear positive result on at least one of the homework items — a session that ends on a specific improvement, however modest, builds both the horse's and the rider's sense of progress and makes the next session's starting point higher than the last.