If someone has ever hurt you, and you have developed a certain hate towards them, lose it now. You see, love and hate are at opposite ends of the spectrum, right? They are two extremes. And both love and hate have one thing in common; taking over your head space. If you love someone, they are all you will think about. If you hate someone, the same goes, just in a negative way - which is much more self-destructive. You need to find the neutral balance in the middle of this spectrum. You need to become apathetic, so this person is nothing but a withering thought in your brain; something trivial, unimportant to your time and effort.
Don’t ever hate anybody, because that is just as bad as loving them.