If I want to just write SOMETHING I'll do some automatic writing. I often get random phrases stuck in my head so I usually start off with one of these and then just... keep going. It doesn't have to make sense it just needs to exist and get you moving. If you get stuck start describing the room, the weather, what you're wearing, what you ate today, etc. being really descriptive with language is always a good exercise.
Tips:
- Don't go into it expecting to write anything good. Maybe you will, maybe you won't, the point is just to write something.
- Don't read it back straight away. Just write and leave it. Come back to it next time you open your journal and see if you can find anything good in there. You might find a good turn of phrase or word you've not used in a while
- Automatic writing is a great way to make use of those words or phrases that you overhear or that get stuck in your head. You might find yourself making sense of them or putting them next to another idea that makes both stronger.