Comment by TomasBM

In addition to other great suggestions (a good night's sleep being #1), two things come to mind:

- Write down thoughts that pop-up and seem potentially useful, and then forget about them. It's easier said than done, but you have to balance "this may seem useful later" with "I got better things to do now". For me, knowing I have the idea recorded somewhere puts my mind at ease.

- Feel free to just get rid of accumulated browser tabs, random to-do's or even mental notes. If you always have multiple things open, do a hard reset every now and then. It's difficult to let go at first, but you may realize that if an idea was really worth entertaining, it will come back to you. No great contribution is the result of one single thought, IMO.

Note: I lean closer to scattered attention than AD(H)D, because it doesn't affect my normal functioning. Sure, it gets progressively more annoying when deadlines are looming, but it also provides a great source of creativity.