What is the best way to fix a horse that rushes through transitions and lacks smoothness?

A horse that rushes transitions — breaking abruptly from walk to trot, launching into the lope, or falling into the halt — has not developed the balance, collection, and attentiveness to the rider's aids that smooth transitions require. Clinton Anderson and Pat Parelli both address transition quality as a measure of the overall quality of the communication between horse and rider. Anderson's approach to improving transition smoothness is through repetition of transitions with very precise timing of the release. The horse that rushes into the trot is rewarded — through release — only when it takes a smooth, balanced first trot step. If it launches or breaks forward abruptly, Anderson immediately returns to walk and asks again. Over many repetitions with consistent criteria, the horse learns that only smooth transitions produce the release. He also addresses the preparation phase of the transition — teaching riders to half-halt or prepare the horse before the transition rather than applying the transition aid cold. A horse that receives a preparation signal — a slight steadying of the seat and reins — before the transition aid has time to balance and organize itself, which produces a smoother departure than a horse asked to transition from no preparation. Parelli frames smooth transitions as an expression of the horse's collection and responsiveness. A horse that is genuinely light and organized — that maintains self-carriage and responds to subtle cues — executes smooth transitions naturally because it has the balance to do so. The horse that rushes transitions has not yet developed that balance, and the path to smooth transitions is collection work rather than drilling the transitions themselves. Warwick Schiller adds the timing component: a horse that anticipates transitions will often smooth out significantly when the rider varies the timing and location of transition requests, because the horse must wait for the actual cue rather than launching into the transition based on the pattern it has learned to anticipate.