That blank page screams at you with all its anxiety for you to fill it in. But starting from scratch can be intimidating, especially when anything goes. It's not surprising that so many aspiring writers quit their canvass–it's so much easier to avoid the pain of inconsistency.
That's where the system comes in. Instead of waiting for inspiration, you set a schedule for the muse to wake up. Whether you can squeeze in an hour between 5 – 7 AM or find time to write during lunch break at work, the practice has to get done. The method is everything. Everything is practice.
What you write isn't as important as the process itself. Some days (i.e., most days), what spews out the ink is garbage. However, nothing goes unused. That weak sentence or kernel of an idea resurface in more lucid prose in the future.
Words are tools for making stuff. And the more one sits down to yank them out of the head and onto paper, screen, whatever–the more likely it is to do it again and keep going regardless of how the person feels. When in doubt, the processes that worked before.
In search of clarity, it only comes through at the result of the work.