It's a little thing, but I think one of the best parts of s/m play is about three quarters of the way through a session, assuming you're following the relatively standard "gently caress the impacted region between blows" protocol, your subject will usually start to flinch away from even just the caresses.
And at this point it's really delightful to mix up the rhythm. Caress, then caress again as if caring delicately for your subject, until it relaxes and then you return to pain again. If it's looking, go to hit then pause at the last second and pivot to gentle contact. Hit suddenly without warning before it can prepare itself.
Really just so lovely. The point at which the subject begins to simply react to your movements automatically. A really special kind of vulnerability, higher order thought ceases and body becomes a vessel channeling my touch. Lovely.