Since I was first able to talk, I have heard about the “Golden Rule”. I have constantly been playing recreational sports since I was four years old, and one of the coaches' rules was always "treat others the way you want to be treated". When I got a little older, my dad expanded that to "do unto others as you would have them do unto you". After thinking about this "Golden Rule", I realized that it is absolutely the most essential rule to live by, and certainly lives up to its name.
If you learn to respect everyone you come across, the respect will be reciprocated, and that will make you both better people. Hatred accomplishes little, except for deepened wounds and hurt feelings. I like to pride myself on the fact that there are very few people who dislike me, and I make a point of not upsetting anyone. Of course, disappointing or hurting people is inevitable, but by treating others with sympathy, and respect, they appreciate my effort and subsequently, return the favor.
The Hebrew Torah's version of this saying is "love your neighbor as yourself". Being Jewish, I hear that verse frequently, and it always rings true. You cannot succeed in life by being an inconsiderate or harsh person. People will lose respect for you, and treat you in much the same way.
Constantly I am reminded of this pertinent saying, and I make an effort to live my life accordingly. Evil and animosity in people cannot be completely prevented, but by "killing them with kindness" and treating them the way you want to be treated, they're likely to soften up. I feel like the "Golden Rule" is every bit as important as the name suggests, and thus is the most important life lesson I have learned.