What's happening
ADHD and half-finished jobs often go together because starting is exciting and finishing is dull. The first coat on the shelf is satisfying. The second coat and cleaning the brushes aren't. So you drift to something newer, and the shelf joins the form you got halfway through and the washing you put on yesterday. Each open job sits at the back of your mind, making it harder to settle on any of them.
How to get moving
Walk round and write down every job you've got on the go, even small ones like a parcel that's half wrapped. Pick a limit, like three open jobs at once. While you're over it, you don't start anything new until you've finished one, and the quickest to finish is usually the best place to begin.
If a job really can't be finished yet, park it properly rather than just walking away. Wrap the brushes in cling film, put the form back in its envelope with a pen clipped to it, and gather the bits into one box or bag. Then write the exact next step on a sticky note and leave it on top, like "second coat, then put the screws back".
Important tip
That sticky note matters more than it looks. When you come back to a half-finished job, the hardest part is working out where you were and what comes next. A note written while it's fresh means you can pick it up in two minutes instead of twenty, rather than giving up and starting something new instead.
This is lived-experience content. It is not a promise that a particular idea will work for everybody.