Offload all the mundane aspects of life into TODO lists in iPhone Reminder app (that are also shared on iPad, and web via iCloud) so that they don't clutter my mind so much. Go through them and execute on tasks whenever you have some otherwise unoccupied time. Have separate lists for different categories of tasks. Mine are currently:

- regular reminders - thing to do soon/soon-ish

- things I need to do at a specific date, but no sooner, set with reminder for that date & time (ex. go pick up car from the mechanic on Friday afternoon)

- recurring reminders (ex. backup laptop weekly, send monthly invoice to client)

- list of stuff I'm waiting for (ex. stuff from amazon, reply to email from client)

- less important stuff to do/explore, whenever I have some free time (ex. try to find comfortable and not terribly-looking 100% waterproof pants so that I can take long walks in the rain)

I also keep a list of recommended media (books, movies, tv series) to consume next.

All in all not terribly original, but it took me a while to arrive at this system, so maybe it'll be helpful for someone.