According to Harvard Medical School keeping a journal can help process the feelings of grief and have some great insights into the process here.
Keeping a journal of letters for someone special is like a never ending love letter to be read and read over again. The gift of handwriting is a generous, thoughtful and priceless legacy of thoughts and feelings.
Keep a couples journal to write about your relationship, either together or seperately. Writing can allow you to articulate things you might not be able to say out loud and can bring you together to open doors for better communication and work through thoughts and feelings and a deeper understanding of each other. It can also be a place to write love notes to each other and work on a strong bond together.
