As I get further on with writing novels it seems to me that flexibility is a useful tool for novelists too. When you get stuck in one particular section, move on to another which looks more promising. Never let it become a drag on the soul. When I was writing A Single to Rome it was ages before I knew what Natalie, the main character, did for a living. So I skipped through the work scenes and came back to them when I'd decided - more than half way through. Apparently, when Mike Myers is gets stuck he simply writes 'And then something amazing happens', and carries on.
For me, the really satisfying moments in writing are the ones where the difficult piece that didn't seem to fit anywhere at all suddenly slots in and the whole picture becomes clearer. So, once I knew what Natalie's job was, a lot of other scenes fitted into place, and a lot of future scenes became clearer. It takes faith, of course, to believe that if you leave a scene half written or sketched in it will resolve itself later. But at least, unlike Sudoku, if you go wrong you don't have to rip it all up and move on to something else.