Casual Conversation

There's lots of schools of thought on how you should write your diary, but imo the most important thing to keep in mind is that diary is for you.

I primarily use my diary as a coping mechanism to deal with stress and to reframe my outlook. This means I don't think very hard about what I'm writing, I'm just putting my feelings onto a page. Then once those thoughts are on paper they become easier to deconstruct.

My primary diary pulls double duty, and I use it to plan out the following day. When I reflect on how today went, it's easier to make a plan for tomorrow. And at least in my experience it's easier to make a plan the day before than to wait and see how I feel the next day.

Some people like a themed diary. I keep a separate gratitude journal where the only rule is to write things in it that made me happy. This is helpful on bad days when I can't think of anything good going on in my life

If you're into mental health and self improvement, there's loads of literature on Cognitive Behavioral Therapy (CBT) online. CBT is the gold standard of psychiatric care currently, and is primarily self directed through journaling exercises. Searching for these exercises could give you a framework if you'd like to follow something a bit more rigid