Conditioning

Classical conditioning is a technique of behavior modification, it uses two different stimuli, one which already causes a certain behavior, and the other which the experimenter wants to begin causing that same behavior. The first stimulus is presented along with the second stimulus, and after enough repetitions, the subject learns to engage in the behavior when the second stimulus is presented alone.
In class, when we were learning about the concept of conditioning, I kept wondering what the limits to this extraordinary method of behavior control were. In a way, it seems like almost all of our behavior is defined by conditioning (that is, almost all of our behavior seems learned), from walking and talking to reading and interacting with people. Even the way we deal with undesirable situations and our own shortcomings seem learned to some extent. For example, if we learn, early on, how to behave a certain way towards certain situations, could those behaviors be changed later on in life by using conditioning techniques? The concept of conditioning is extremely important, in that, it has countless practical implications and uses. One such use is (famously) discussed in the fictional book (and movie) A Clockwork Orange. In the movie, a brazen and habitual criminal is put in prison and is selected to be part of an experiment regarding conditioning and criminal behavior. He's put through a series of treatments that couple a deathly sick feeling with videos of rape and violence. After treatment, he cannot stand to hurt another person, even if that person is harming him. The conditioned response (sick feeling) always outweighs the potential benefits of engaging in rape or violence. Of course, the conditioned response does not need to be a punishment, but the example in A Clockwork Orange still a good example of using conditioning for practical purposes.
The idea of conditioning became even more interesting when I began learning about Oxytocin and Vasopressin (hormones associated with love and companionship) in my biology class. If conditioning is really as powerful as I've read, could someone hypothetically control the hormone balance while presenting specific stimuli to the subject in order to significantly encourage certain behaviors like helping others or working hard? If I wanted to love exercising, but didn't, would taking a Vasopressin supplement while exercising help?