Having anger and hatred in your system is not good for you. I am a prime example after being angry and hateful most of my life I know all too well what it does to a person. It causes issues mentally and physically. It makes being with other people difficult because the littlest thing can make you go over the edge.
Wanting revenge is also a sign of hatred against the people you hate, but some people take it to the next level. Some people actually methodically plan out revenge, and if successful it lasts for a few minutes for the guilt to set in. That way to go is not advisable because the legal system is a pain in the ass taking days out of your life in court. Not worth it.
There is another way to deal with those emotions though. Writing about it. Not using actual names of course, but taking the emotions and using them for something good and constructive. Writing about the situation that you are angry about or the types of people that make you hate or angry, and continually bashing it over and over again until it goes away. Writing about people getting it because of what they said and did. I thought if I ignore the bad things it would go away, but no it turns out it is here to stay.
That is how I found my strength writing about the darker stuff until it does not bother me. I found those emotions as a catalyst to boost me to the next level. I use it like fuel making me write, and that is the reason why I do not feel like writing because I hated those emotions. That is probably the thing that is going to up my writing to the next level because I am turning those emotions into something constructive instead of destructive. I finally accepted what kind of writing I am good at, and how to handle certain emotions instead of letting it ruin my life.