When I was growing up, crossword puzzles were among the unfathomable pleasures of grown-ups. My grandmother would sit in her den for hours, the puzzle in her lap, looking blankly around the room as if she had just read a piece of news whose enormity she could scarcely comprehend. Other adults would drift by to offer their condolences ("A nine-letter religious figure, hmm") and I would stare from the rug in disbelieving boredom.

My conversion to a crossword puzzler, then - and not just any puzzler but one who has favourite puzzlemakers - has required a bit of an inner adjustment.

To my 10-year-old self, I can say only: Forgive me. And perhaps more defensibly: Crossword puzzles turn out to be great practice for one of the few endeavours that both of us can respect - fiction-writing. In fact, it can provide a crucial map of the strange terrain of this profession. Here are some of the landmarks.

THE BLANK BEGINNING

You sit down with a Saturday puzzle, you cheerfully raise your pencil (or pen, depending on your arrogance or foolishness) and... nothing. The clues are a forbidding mix of foreign rivers and inscrutable opera references.

But then, after a few minutes of dumbfounded staring - you don't have a breakthrough, exactly, but you glimpse a possibility. You somehow hadn't seen this "It's a burden" clue, and you aren't certain that it's ONUS, but it's the right length, and it's not as if you've anything else going. And before too long you're under way.

The equivalent blank period in novel writing can, unfortunately, last months or even years. There will be stretches in which the only characters you're able to summon arrive faceless or, worse, voiceless. These are the times when you'd start Googling law school application deadlines if it weren't for the memory of that Saturday puzzle: Even a granite wall, studied with sufficient patience, reveals its cracks.

THE WALK-AWAY

Once you've made some progress in a puzzle, however halting, a certain pleasurable momentum begins to build. You begin to wonder if this is the year when you'll enter the American Crossword Puzzle Tournament, until ... You come face to face with the part of the puzzle that refuses to give. All you've got is FARMLAND, and this FARMLAND seems to have been salted.

I can't emphasise strongly enough what you should do at this point: Walk away. No matter how loudly the stubborn sectors of your brain insist that just a few more minutes of concerted staring will do the trick. Sometimes, after an hour or two away, I'll find the answers coming in such a cascade I hardly have time to wonder what kind of idiot was working on the puzzle before.

And so it is in writing. I can count on one elbow the number of good writing ideas I've had while straining at the keyboard. When you find yourself stumped, when a character seems to want to do this but the story seems to demand that she do that, it's time to go for a walk. The answer will pop up into your mind so unexpectedly that you will very likely not be carrying a pen.

THE DAM BREAKAGE

At some point in every worthy puzzle there comes a moment when you realise that there has been, all along, a huge mistaken answer at the centre of your grid. For an hour you've considered every possibility - a misprint, a conspiracy, an unprecedented lapse into Esperanto - except that the answer itself could be wrong. When it finally occurs to you to erase it, the sensation is as of a river suddenly running free.

In novels, too, it is very often the most basic decisions that turn out to be the problem. It isn't his neighbour who comes over; it's his brother. They aren't going to meet their adopted child's parents; they are the parents. The pain of undoing months of work is nothing compared with the feeling of sudden freedom.

THE SLOW CLAP

Towards the end of a puzzle, there's a moment when you shift from being the puzzlemaker's adversary to being her admirer, even her accomplice. The human intelligence on the other side of the page begins to come clear, and you shake your head in weary wonder that you could ever have wished to set this beautiful puzzle on fire.

In fiction writing, you are of course both the maker and the solver, but the sense of discovery - the feeling that whole sublayers of structure and theme have been created by a stranger with your pleasure in mind - is no less acute. So this is why I had him be a dentist. This is why it matters that her father grew up in Spain.

And this, you think - until the next book, the next puzzle, appears, and the whole maddening cycle begins again - is why I became a writer. NEW YORK TIMES

•This is an excerpt from the final essay in Draft, a series about writing, at nytimes.com/opinion.