The feeling of total euphoria when you batter down those walls, though. I finally cracked something yesterday that has been a major stumbling block for eighteen months; I kept putting it to one side and working on other parts of the jigsaw, but now that I've kicked the wall down I can't stop grinning at people in the street.
Don't lose heart - the answers are nearly always there, somewhere, and the good people on here are so helpful and knowledgeable.