There have been a lot of warning signs that I should quit my job. Events at work; my reaction at night to events during the day; the fact that my last vacation was the least relaxing vacation I can ever remember. (And the vacation before that was interrupted by news that a coworker/friend was probably quitting.)
The strongest recent warning sign, though, was Agile Open California. I go to that conference every year, it's one of my favorites, it always fills me with energy and ideas. Not this year, though: I was mentally checked out for most of the conference, and the main thing that I got out of it was the name 'Mini Waterfall' to describe the way we'd done our iteration planning from the middle of 2011 to the middle of 2012. (After which we switched to an awful Kanban implementation—the awfulness was in large part my fault—and instead of trying to improve that, we switched this fall to a 'Mini Matrix' planning/team model. Whee.)
I'm only having fun if I'm learning stuff. And I'm also a much more productive employee if I'm learning stuff: if my brain is working actively, good things generally happen around me (albeit unpredictable good things, mixed in with a bit of bad), whereas if I'm just going on autopilot, then a company can find a fair number of people that are as productive as I am. So, if I'm seeing signs that my learning pathways are actively blocked up, that's really bad.
Fortunately, Agile Open California provided a solution to my problem to go along with that diagnosis: a key part of any open space gathering is the Law of Two Feet, which states that:
If at any time during our time together you find yourself in any situation where you are neither learning nor contributing, use your two feet, go someplace else.