If you feel the need to get back at your ex, you need to know how to control your resentment.
Managing resentment is about knowing what resentment and anger are and how they are different.
Anger is a feeling that is used to make you stand up for your rights and to sustain your ego, therefore anger is a signal that is used to encourage you to take a course of action.
If you ignore this message or signal numerous times without taking any action, there will be hatred directed towards the person who caused you harm, the feeling of helplessness and frustration will grow.
The combination of these three factors:

1. hatred
2. helplessness
3. and frustration

is what is known as resentment.
Resentment and acceptance In the area of personal development, there is a school of thought that is widely misunderstood, the school of "acceptance".
This school believes that acceptance can only succeed if you have the power to take back your rights and not when you are vulnerable and have no other alternatives.
Our mind can only recognize acceptance as an answer when there are alternatives, but if there are no other solutions aside from acceptance, then it will not work.
For example, everyday your neighbour gives you a slap, can you persuade your mind to agree to it or accept it? This can never occur because your mind in this situation will know that you are attempting to accept it since you are helpless and have no other course of action.
Acceptance can be a way to dealing with resentment; however it can only take place when you have other options and not when you are helpless.

1. Resentment and helplessness: If ever you choose to accept what occurred or to exercise your rights, you must first believe that you are not powerless and that there are available alternatives.
   For example, your supervisor screams at you every morning.
   What you should do is to go one day and boldly and professionally speak up about your concerns.
   By speaking out, you will realize that you are in control and that other options are available aside from bottling the anger, it will be sufficient to ease your resentment.
   
2. Resentment and gossip: Resentment is a form of helplessness, so much so that some people use gossip to get revenge.
   The ones that use gossip as a form of revenge are those who have unresolved issues with someone and were not able to complete it face to face.
   They found no other solution aside from completing it behind them.
   They perfect way to release any of your feelings of resentment is to confront the person face to face.
   
3. Resentment against life: Some people who have failed to achieve their goals might become resentful towards everything or everyone around them.
   The disappointment they carry is released now and again in the form of anger.
   They must learn to ascertain the root of their resentment and exert all their efforts towards changing or accepting that reason, instead of wasting energy on unrelated things.
   When you cease being helpless, you stop being resentful.
   

When you know how to banish resentment from your life, thoughts of getting back at your ex will be banished also.