Idly window-shopping for a desktop computer. Not 'cuz I need one; just 'cuz. Idly lusting after a $4,000 setup.
Then my brain sez, "OOH! OOH! You should totally check out that discount computer website you sometimes go to--maybe they will have the EXACT SAME THING for, oh, say, fifty bucks!"
So I went to their site.
Turns out they did NOT have a $4,000 setup for fifty bucks.
Moral: Don't listen to my brain. It's really full of it.