I found it best to put a topic at the top of the page, write a brief paragraph of what it's about in more detail, (the event that is causing pain or hurt or anger), and start processing the 4 basic feelings:
I feel angry that . . . then feel it all and move to: sad, afraid, guilty. I always end it on the positive though: pain of this is I cannot change the past, but I can now [find some positive feeling]: have learned a lot through this experience. . . have greater trust in myself . . . etc. whatever feels right to you.
I found that as I started writing, more and more came to me so it flowed once I got started.