When you scour Asian art museums for any mention of the game of Go.
Counting territory on your salami pizza toppings!
You hate this god damn game, but keep playing because you love it.
After a game with a friend, he unsuccessfully tries to convince you that “there is no such thing a Sente or Tenuki”, because “this is CHESS goddammit!”.
“Everything in excess; moderation is for monks!”
The road of excess leads to the palace of wisdom. - William Blake
When you start to “forget” boards and stones in nearby guesthouses or bars/tea houses. Well they could be more useful there at least.
Which may come with teaching the game to the owner, waitress and the cleaning woman.
When the only clever and enjoyable gift you want to offer at every Christmas/birthday/anniversary let it be the 50 years of wedding of your aunt or a new addition in the neighbors family has to be a go set.
…when your main reason to start new hobbies(poker, chess, running, etc)/try new activities is to improve yourself for studying go.
…when you find it difficult to take a hiatus (for the sake of improving upon return) because you’re not sure what you’ll do with your time if you aren’t playing go.