Another interesting idea: apparently, positive motivation (reward) works much better than negative motivation (punishment). Allegedly it's "scientifically proven" (for some definition of "scientifically") which I haven't yet taken the time to research, but I plan to. I've been thinking about how to apply this in two of the most important areas of interpersonal interaction in our lives, in our careers and in interpers…
Rewards can also backfire. I'm currently reading "Punished by Rewards", by Alfie Kohn, which spells out all the ways in which rewards are counterproductive. Interestingly enough, I found this book via Marshall Rosenberg's book on non-violent communication, in which Marshall urges us not to use rewards as a means to manipulate others (and not to use punishments for that purpose either of course).
Can that (i.e. non-manipulative rewarding behaviour) still backfire? Probably, although I'm then not sure what the solution is... to influence reality and your own well-being, you have act, and even the most fail-safe behaviour (like not spending time with a person anymore) is described by the above framework (i.e. it's a type of punishment), and furthermore it's not always possible (e.g. with children, or if you want a job and a relationship, most people seem to).