I urge them to ignore every grammar and spelling rule. Experimenting with warm-ups. Some clients feel more comfortable keeping a journal to track their thoughts before writing a letter. For those who panic at the sight of any blank page, I suggest they start out by talking into a tape recorder. Nothing cast in stone.
Some clients feel intimidated by the permanence of writing.
I find it helps to remind people that whatever they write is simply a snapshot of where they are with their concerns right now, today. This may change tomorrow. Jonathan Diamond's book, Narrative Means to Sober Ends, is now available in Canada.