Reaction formation takes place when a person takes the opposite approach consciously compared to what that person wants unconsciously.
For example, someone may engage in violence against another race because, that person claims, the members of the race are inferior, when unconsciously it is that very person who feels inferior.
Psychological projection occurs when a person "projects" his or her own undesirable thoughts, motivations, desires, feelings — basically parts of oneself — onto someone or something else. Since the person is experiencing particular desires, feelings, thoughts, or anxieties, s/he is more prone to attribute those same characteristics to the thoughts, feelings, and motivations of others.
Rationalization involves constructing a logical justification for a decision that was originally arrived at through a different mental process.
For example, Jim may drink red wine because he is an alcoholic, but he tells himself he drinks it because it has some health benefits, in order to avoid facing his alcoholism.