In one of Parry's lectures he played all the sketches Beethoven made for the 'Eroica' Funeral March (first theme). Sketch no 1 was not at all bad. No 3 was beautiful. No 6 was stupid. No 9 was bloody. The final one was a return to no 3. The moral of which is that if you spoil good stuff by working at it you must spoil the spoilation by more work.