The importance of mental structures shines when you aren’t at your best.
Good mental structure helps mitigate risk when life throws curves. Since, as a creative, you have to thrive on that ambiguity, you’ll have to trust that structure more than the average person.
When you are building some structure in your life, it is ugly. It’s slow, never smooth, and filled with failure. In the end, however, you’ll have another tool in your kit that will help you get work out the door.
You still have to ship, because, as a professional, you can’t relate to waiting until inspiration strikes.