In his writer's notebook, 1932-1933, Henry Miller, an author with a deep sense of process, laid down his ‘commandments' of writing. Here they are adapted to whatever it is you want to create:

• Work on one thing at a time until finished.
• Don’t be nervous. Work calmly, joyously, recklessly on whatever is in hand.
• Work according to The Program (the timetable you've laid out for yourself) and not according to mood. Stop at the appointed time!
• When you can’t create you can work.
• Cement a little every day, rather than add new fertilizers.
• Keep human! See people, go places, drink if you feel like it.
• Don’t be a draught-horse! Work with pleasure only.
• Discard The Program when you feel like it — but go back to it next day. Concentrate. Narrow down. Exclude.
• Forget the next thing you want to create. Think only of what you are creating now.
• Do it first, always. Painting, music, friends, cinema — all these come after.

You can find Miller's original and The Program here.