Mental Health America had a webinar on journal writing a month or so ago. You can view the video and download the PDF at this link: Writing Through Lived Experience: Writing to Support Your Mental Health Journey | Mental Health America.

Some ways they recommend getting started include:
* Write for 3 minutes about how you feel, without stopping.
* Ask yourself a question and then write out your answer and how you feel about it.
* Write a letter either to your future self or someone in your life.

You don't have to ever let anyone read what you write. It is mainly to help you think things out and I think the writing helps you become more aware of what you are thinking.