I'm always going back. And, as Skibble suggests, I also keep notes (a fairly detailed time-line in particular). But going back, sometimes just a little way, sometimes a long way, I find helps to get me back into a consistent frame of mind (consistent with where I was when I was writing before). I don't consider this going back to be editing, although some changes do get made as part of that process, they are changes related to how it flows (and "feels", without trying to sound too mystic about it) rather than looking to correct technical issues. I reserve the technical sort of stuff for after I'm finished the first draft.
Whether this going back over would help you depends on what sort of writer you are (or will turn out to be), and just how lost you've become. You may even find you're really an outline person, and so now might be the time to write an outline of what you've got so far and see if that helps you.