The Writing Life is Strange

I'm sitting here after spending a great deal of time rewriting a couple of chapters.  I'm taking a writing course at RWA on writing suspense.  So far it seems common sense lessons, but sure enough after reading what I've written so far on Murderous Visions, I found some things that needed to be added/changed.  I don't mind.  Lord knows I want to write the best story I can.  But what is that makes us sit down and let the words flow as they will, knowing that you're leaving out some things that will have to be added later, or things that will have to be changed or even deleted.  Here is what I think.  If I (maybe not you) have to keep rethinking as I write, I will get frustrated and give up on the story.  I need to write it as my brain sees it at that moment or the Muse will go off on a tangent (read vacation). So I will write the bones of the story, enjoy writing without rules, and finish the first draft.  Then I will go back and unbreak rules (or not, if I think it works as is), add in "how does that make her/him feel?" and describe the world I've created for my characters.  And if SBP is ready to take me on again, Murderous Visions will be my next book.  I'll keep you updated.