For one thing people tend to be rather forgetful concerning their former state. They change and then they will often deny that they ever had any problem. What seemed like a big ugly issue when they had it, now seems really small and insignificant to them. They will often say that there was never anything wrong, it was just a mis-understanding. And that is quite right for that matter; all we did was to clear up a few mis-understandings. But for sure there is change happening, and it is advisable to record the state of affairs in writing along the way to show what has happened. If we don't keep the record along the way, the evidence tends to disappear.
If we ask the client to give written progress reports, that will also provide valuable information for the facilitator that she might not have picked up on otherwise. People express themselves differently in writing. Sometimes they are more honest, sometimes they have a bigger overview, or it might be totally the other way around.
What I have found useful is to use a form with two sections to it. The top section is for the client to note down what she has noticed she has gotten out of the processing so far, what has changed and improved. The bottom section is for the stuff that she notices has still not been handled or improved satisfactorily.
Asking for both plusses and minuses encourages the client to be more honest, and it emphasizes that we are in the middle of an ongoing process of change.
I will ask the client to fill in the form at regular intervals, usually when we have finished a major issue or a module. I would only bring out the form when I am confident she will have something to write down.
Some people have a bit of a paranoia about being called upon to give a status report. Therefore I want to be sure that we both know that they have chanced. Sometimes a client will change, but if we put a spotlight on their change they will start denying it. That is because they have made the change sub-consciously, but consciously they are still dragging their heels. I would not ask for a progress report before the conscious part of the person is at least somewhat appreciative of what has gone on.
Keep the progress forms in the client's case file to illustrate her progress. You might also want to make photocopies and keep those together elsewhere to keep track of your own results with clients.
Positive statements, or before/after scenarios from the forms can also be useful as promotional material to show potential clients what kind of results are possible. Be sure to get permission before you spread anything around. If the client doesn't give permission, the progress form remains a part of the confidential notes for the client.