When you finish your novel - put it in drawer for as long as you can manage. A year or more is ideal - but even three months will do. You need a certain head on your shoulders to edit a novel, and it's not the head of a writer in the thick of it, nor the head of a professional editor who's read it in twelve different versions.
Sounds like good advice, and it's been almost a year. Having read it again I find myself quickly 'in the thick of it' and motivated to keep going....