1. A pacing therapy system, comprising: an external communication device; a stimulation device adapted to communicate with the external communication device, the stimulation device comprising: one or more electrodes adapted to be placed on or near a nerve of an autonomic nervous system; a sensor that senses at least one of a physiological signal or a physical signal; a processing circuit that provides at least one of a current physiological level or a current physical level using the sensor; and a control circuit that causes the stimulation device to provide a stimulation according to a set of stimulation parameters; wherein the control circuit comprises a memory having a state transition model comprising a transition matrix and a connection matrix stored thereon, the transition matrix definition conditions for transitioning between particular states of a plurality of states of the state transition model and the connection matrix defining whether transitions between particular pairs of states are permitted, wherein the plurality of states are defined by a set of stimulation parameters and at least one of an expected physiological response or an expected physical response during application of the stimulation with the set of stimulation parameters, and wherein the control circuit is adapted to use the state transition model to modify stimulation parameters to bring the at least one of the current physiological level or the current physical level to a reference level; and wherein the control circuit is initialized from a learning phase whereby at least one of an actual physiological level or an actual physical level is determined and stored for a predetermined set of stimulation parameters used during the learning phase.