I end each day by writing everything on my mind in a journal. Todos, ideas to explore, details about work in progress, people to talk to, etc. Very stream-of-consciousness, no filter, no organization. Just get it all on the page.

Every time I find myself thinking about work in the evening, I walk back over to my desk and add to the journal entry.

I find the biggest cause (for me) is having ideas bouncing around in my head that don't exist elsewhere. Maybe it's an idea that's not concrete enough to become a Jira ticket yet, or a vague sense that "we should do thing X". Once it's written I can forget about it, and pick it up the next morning.