Yeh, sometimes it all comes together with the first render.
Other times... well f**k it all.
I'm just saying that there is a time to re-start  the whole process.
Start with default lighting, and gradually build up the scene all over.
Is that so unreasonable?
I have lots of HD space, but what's the poin tof keping  crap? For crap's sake?
Out with the old, start again is my motto.
Often it will give you a whole new perspective.