When every time you see another one in public, you subconsciously note if it has JDM tails, the S2000 antenna conversion, TRD spats, etc.
When you refresh the classifieds forum once a day waiting for "FS: Projector headlights - $120 shipped".
When you can tell how much people know about cars based on the first question they ask about yours ("Is that a Supra/GT-Four?" vs. "Nice Celica, but what hood is that?").
When you buy a GT-Four in Forza Horizon 2 (which takes place in Italy) and wonder why they made it RHD and included a full Vis body kit for it, but they didn't go the full length to put in the JDM headlights or taillights.
When you see a 7th gen in public and wonder if they realize how much better looking your 6th gen is.
When you initially bought it just because it was cheap, had a nice "rally" stance, and had great online reviews, but you quickly realized just how much potential it actually has. I've only owned mine for about 5 months, and I'm already way sucked in to the lore behind it.
When you have a "favorite" 6th gen owned by someone on here who can actually afford serious mods.
When it's the first car you've owned that makes you realize all the hype about importing parts from other domestic markets.
And finally, when your girlfriend hates it because it's "too 90's".

Just wait until I buy confetti seats...