Read patterns, not one bad day
Track repeated drops in performance, persistent joint irritation, sleep disruption, and loss of enthusiasm. A single flat session is information; a trend requires change.
Reduce sets or demanding exercises before abandoning the entire method.
Soreness is not the score
Novel movements and long muscle lengths can create soreness without proving the session was better. The goal is useful work you can repeat.
Eat adequately, sleep consistently, and keep easy days genuinely easier.