[Serious] I have constantly been told that keeping a journal can help with mental issues. Does it work for you?

I have constantly been told by therapists, etc, that keeping a journal can help you overcome anxieties, sleep problems, and the like. I've been struggling with it, where I'll be so stressed out I'll be up for days at a time. Many times have a tried to keep a journal, and many times I have failed.

Is there anyone who has maintained a journal for a long period of time? If so, does it help? How do you manage to find shit to write about every single day to make yourself feel better?