A very simple principle in life is that it is probably a good idea to be associated with the stuff one wants and dissociated from the stuff one doesn't want. And that is basically also what we are trying to accomplish in processing: more of what the person wants, and less of what she doesn't want.
Good feelings, abilities and desirable qualities are of most value if one has them. They are most useful right "here" not "over there". You feel things right where you are, and most likely you desire to feel good.
Bad feelings, negative experiences, and problems aren't much fun to have. They might be more useful as learning experiences if one can keep a certain distance to them. Knowing about them without having to live them.
There is of course more to it than that. "Negative" stuff isn't negative anymore when we dig into it and find out what it is really about, and any experience has a valid reason for being there. So, it is not as simple as just getting rid of the "bad" stuff. But there is no reason you should feel forced to continuously endure the worst effects of what is there in your life. You have the right to decide where you put things in your life, and where you put things in relation to them.
The problem is when one gets stuck in one mode or the other. The trouble with traumatic incidents is when one stays permanently associated into one, replaying it in the present, even though it was done a long time ago. Incident re-experiencing remedies that by dissociating specific incidents. They are turned from an ongoing active mechanism into a learning experience.
A person who is stuck in a dissociated mode, analyzing everything mentally and not getting into the emotions of anything, is not much better off. She needs to learn how to associate into things, how to contact stuff she wants and get excited about it.
The ability to associate or dissociate at will is a very worthwhile ability to develop. Hopefully we will accomplish that through the processing we do with people. To accomplish that, you need to do both, of course. Just dissociating people from everything doesn't teach them to associate.
You can apply this directly to any reality that the client has trouble with. If she feels stuck in a certain way of being and you can get her to see herself from a distance like that, then you have just moved her from associated to dissociated. Working with the perceptual distinctions is your main tool here.
Dissociation involves distance. One sees the events or the pictures "over there". Pictures are easy to move around and associate or dissociate, but it is usually the feelings one would really need to do it with. We can use visual distinctions to manipulate things with. If you see your body from the outside, you are dissociated. If you see things out of your eyes, you are associated. If the body feels something unpleasant, the situation will be more comfortable seen from the outside.
A feeling can also often be dissociated by assigning visual qualities to it directly. An unwanted body feeling can be assigned a color and then moved around. Like:
C: "I have a headache"
F: "What color is it?"
F: "OK, change it to green"
F: "Good, now move it over on the wall"
F: "And put it outside the window"
C: "Oh, by the way, I don't feel the headache any more"
That is a simple trick that can be done anywhere if you don't have time to dig more into the matter. It doesn't tell us much about why it was there, but it does sometimes give relief of the pain.
A person's body language changes depending on whether she is associated or dissociated. A dissociated person is likely to lean back and focus her eyes further away. An associated person is often leaning forward and focusing her eyes inward. You can notice the change when your client moves from one state to the other.
Simply put, we are working at having the client dissociated from stuff that doesn't serve her, and associated into empowering feelings and abilities that she can use in life.
Usually association is the most desirable state to be in in the present and dissociation is most applicable for the past and the future.
A future desirable reality is often more attractive if it is presented in a dissociated way. If it is visualized associated there is not much incentive for working on getting it. If it is dissociated, one can see what one wants, but it is also clear that one doesn't have it yet.