My teacher suggested I keep a journal to jot down my thoughts and insight from meditation. It's a good way to keep track of what is going on in your mind and note any progress/changes you discover.
That's kinda my take as well.
I'm not particulary interested in "progress" as such, although I think it might be difficult to not end up including at least a display of progress even if not intending to do so.
Nothing wrong with "progressing" on the path, of course, but I just don't want it to become an ego thing, like "OMG I have progressed like SO far! SEE?"
Although I don't enter retreat for another week, I'm thinking I may start the journal in the next day or two.
BTW, do you actually keep a journal yourself?