“You shall not hate your brother in your heart. You shall reprove your fellow and do not bear a sin because of him.” Leviticus 19:17
The sentence preceding the “Golden Rule” deals with the prohibition of an emotion: we’re not to harbor hatred [in our hearts] for our fellow man [from a wrong done]. These two sentences should not be understood not as two separate mitzvot [as they often are], because the latter sentence affects our ability to perform the first.
In compassion, Torah tells us to extinguish hatred once it pollutes our hearts. [Interestingly, my Psychology class provides the same answer: Cognitive Dissonance.] As we know, hatred destroys relationships but talking draws people together. Therefore, Torah tells us, “Do not harbor feelings of hatred; instead, talk with your brother so the issues can be resolved and the building of a positive relationship will end your sin of heartfelt hatred on his account.” Once accomplished, you can move on to showing love to your neighbor and the past issues will soon be forgotten.
 Artscroll Chumash, ©1993-2003, page 661
 When a person’s behavior is not in synch with an emotion, tension and dissonance are created and the mind seeks to balance the incongruence and, generally, the activity overwhelms and realigns the emotions to accord with the current action.
 Leviticus 19:18