Doing crossword puzzles in pen is a dangerous sign of
hubris. If you think you're so dang
infallible, be warned--the
gods frown on
mere mortals who attempt to
scale the heights of the New York Times Sunday Crossword without an
eraser.
You may also refer to the immortal words of Proverbs XVI.18--
Pride goeth before destruction, and an haughty spirit before a fall.
Of course, if you can't find a pencil, go ahead and use the pen. Just don't say I didn't warn you.