This is an odd, out-of-sequence post, but I just saw this and thought it needed sharing.
@crypticpaul - John Halpern in real life - is one of my heroes. I'd rate him comfortably among the top five crossword compilers in the UK (possibly the world), and not just because he has the same kind of juvenile sense of humour as I do.
I was particularly taken by his main point towards the end: that puzzles encourage you to get used to being wrong and making errors. If a Paul puzzle defeats me, I shake my fist and say "I'll get you next time, Halpern!" rather than "I must be rubbish at crosswords." And that's exactly the attitude you need to be a good mathematician.