As a retired trauma counselor specialized in working with sexual abuse survivors and battered women I would strongly recommend that you do a lot of reading on emotional and psychological trauma.
Working with clients who have been traumatized is a challenge but it can be done if you have a lot of patience and empathy and if the person is ready to really address the issues and make small changes. I learned that most people who have been traumatized take very tiny steps forward and each step needs to be commended.
I use the application of trauma when dealing with ex-cult survivors because they have lost everything: family, friends, their emotional support systems and even their faith. For many the loss is immediate, when they are disfellowshipped for example. That is traumatic and it needs to be seen that way.
Many ex-JWs sat on the fence and had started to build up friendships and a support system before they left but it would still be traumatic to have a parent or other relative terminate all contact.
Telling a person who has been raped or run over by a truck to "move on" simply won't work. For a therapist working in any field that deals with trauma to even entertain the idea that people should "move on" negates their experience and their feelings about what they have gone through. And that can be just as traumatic. And believe me they will sense any negative emotions you may have.
One thing I learned early on was that if I had not dealt with an issue then I could not help my client deal with it. That means get into therapy and deal with those issues.
Getting on with your life is not the same as moving on when it comes to trauma. I have spoken with many people who left the JWs decades ago, had careers, a family and then one day it hits them and they find they have an issue to deal with. Often there are triggers for this, for example the death of a JW parent where the ex-JW may be told and invited to the funeral but is treated like they are invisible, or not allowed into the hall where the funeral talk is given or not even being told about the death until years later. Each of these situations are going to trigger another episode of issues to deal with. And its not like they haven't moved on with their lives. But events have a way of triggering issues from the past.
I have seen people stay stuck simply because they are afraid of the pain that might surface when they start to examine those old hurts. Someone above mentioned anger. Anger is natural but people often need help in finding safe ways to express that anger. And people who stay stuck in the anger are often even more afraid of the pain underneath it, abandonment is a huge pain that most ex-JWs will have to face.
Your job as a counselor is to guide a person through their anger and pain, helping them to find safe ways to express them and then help them build or use whatever support system they have. Make sure you have your own support system. I worked for 13 years on my own and it is very hard. I had to develop a support system with other professionals who very often did not grasp the enormity of the problems my clients faced. So I made sure I had ways to care for myself.
I did not help every person who came to me. Knowing my limitations was very important and that if I thought I could not help a person then I had to refer them to someone else. That was hard but essential for them and for me.
I hope some of this is useful to you. Use what works and throw out the rest