According to the dual-process theory, which explains responses that occur as a result of two different processes, habituation and sensitization are opposite dynamics that relate to our reaction to stimuli.
Habituation, which may result in a habit or learning, is a decreased response to stimulus as opposed to its antithesis in sensitization: a heightened response to stimulus.
These two reactions are results of different processes, the S-R system and the state of arousal system, and originate in different areas of the human brain. When we habituate, we no longer respond to either the negative or the positive factors of the stimulus. We adapt in a way that we perform a function without stimulus response. Habituation is the result of changing neurons that moderate our level of response. Sensitization occurs when the state of arousal is greater in the excitation of stimulus response. Since habituation and sensitisation stimulus responses have two different results and function through two different systems (S-R and state), they are not said to be related to each other.
An example of habituation is eating in shift-workers who have a set time for their hunger stimulus that is not the same as that of regular workers. The shift-workers' schedules habituate their bodies to change the original bio-clock stimulus. Keep in mind that habituation can be either short or long term differentiating between short-term habituation and long-term habituation.
Sensitization is the excitation of sensory response towards a stimulus. In the example of animal trainers, sensitization is the best conduit to instill trust and motivation in the animal who is being behaviorally conditioned. Hence, a piece of food is often used as a reward for performing the expected response as part of the heightened sensitization process.