If you hate your enemies, you will contract such a vicious habit of mind, as by degrees will break out upon those who are your friends, or those who are indifferent to you.

Hatred does not stay where you aim it. Practised often enough against someone who deserves it, the suspicion and the sharpness become the way your mind works, and they start showing up in conversations with people you love. The damage falls mostly on the person doing the hating, which is the unfair part.

You can oppose someone effectively without carrying them around. Deal with what they actually do, take the practical steps, and refuse them the hours after work. Notice whether your tone at home has started to sound like the tone you use about them.