When you start to refer to real life photos as screenshots. (I do this far too often

)
When you find yourself opening your internet browser and going to the bethesda official forums subconsciously, without ever thinking about it.
When you have a notebook full of quest ideas that you carry around in case you get struck with a sudden quest idea or a twist in a one you already have. (I've done this lol)
When you have to create a sleep package in the CS and add it to your "Self" NPC to finally stop modding and go to sleep.
When you start to wonder what the alchemical effects of a real-life plant are.
When you wish you could use fast travel instead of sitting in traffic.
When you find your game has crashed because you have reached the maximum .esp count in your data folder.
When you can't stop checking your newest mod's download page at least every hour to see what the download count is now.
When you mix up oblivion scripting with other programming languages. (I've started a java program for school with scn name and begin gamemode on accident before

)
When you cry once you realize your entire mod has been wiped out by a hard drive failure. (any self respecting modder would xD )