It's a lot easier than I initially thought: just write down a high-level, abstract sentence fragment of what needs to be done. Get it off your chest and put it in ink (or pixels?). Then ask yourself: how can I split this into two parts? Rinse and repeat.
The initial limiter for me was anxiety and fear about it. Once I got into the habit, the limiter was avoiding hyperfocus and micromanaging myself in the project plan. I try not to break things down beyond 1-2 hour tasks.
This is a good one that often goes unspoken. It enforces role play.