How do you maintain desensitization over time and prevent horses from reverting to old fears?

Desensitization is not a one-time achievement — it requires maintenance to remain reliable, and Clinton Anderson is specific about this because horse owners who desensitize a horse thoroughly and then stop practicing are often surprised when the horse reverts several months later. Anderson's explanation of reversion is straightforward: the nervous system pathways that produce the fear response do not disappear through desensitization — they are inhibited by competing pathways built through positive experience. If the positive experience pathways are not maintained through practice, they weaken relative to the original fear pathways, and the fear response can re-emerge even years after apparently successful desensitization. His maintenance recommendation is incorporating desensitization work into regular training sessions rather than treating it as a separate project that is completed and then set aside. Every session should include brief exposure to previously desensitized stimuli — swinging the flag, walking over the tarp, working near a plastic bag — as a warm-up or cool-down component. Five minutes of maintenance desensitization at the beginning or end of each session keeps the horse's habituation fresh without requiring dedicated desensitization sessions. Warwick Schiller's perspective adds that horses with higher baseline anxiety levels will revert more quickly than calmer horses because their nervous systems are more reactive in general. For these horses, maintaining desensitization requires more frequent practice, and he recommends integrating desensitization contexts into daily handling rather than only in formal training sessions. Parelli frames maintenance as keeping the Friendly Game active throughout the horse's life — his Seven Games framework treats desensitization as an ongoing conversation rather than a checklist item, and his Levels system revisits foundational desensitization work at each new level as a maintenance component rather than a remedial one.