"In these endeavors we do not need to know HOW magic works, only that it does. We prove this by doing the work, recording the results and sharing our information with other magicians" -- Grant Morrison I have always found these two sentences to be contradictory. It seems to me that if you want to do the work, record results, and share information, you necessarily do need to know how magic works. If you don't know how it works, how can you really know if it worked at all? For that matter, I also think you need to know why you're doing a magical process, spell, or working.
From my own experience, it seems that when you understand your personal readings for doing any kind of activity, it makes it that much easier to do the activity consistently, as well as get results that you want from it. When you don't know why you're doing something, not all of you is fully behind doing it. If you don't understand the benefit of doing an activity, then even when you do it, you won't really know if it's actually gotten what you wanted from it.
Knowing why and how to do something is essential for understanding the value of it within your life. It's not enough to simply do it, if you don't understand where that activity fits into the living of your life.