Sick and tired of being sick and tired is a classic.
My most recent "enough is enough" moment was... just really embarrassing and disruptive.. It ties in to being "SICK and tired", I'll leave it at that. So it wasn't a big catastrophe, like a car crash or a death or being thrown in jail or going bankrupt, but it was bad enough to make me go WHAT THE **** ALREADY?!
The big things are the more powerful motivators and tend to push you in to getting help but they don't mean your sobriety is going to last. Whether you are forced to quit or you are just sick of being stuck in the loop, you still have to put in a hell of a lot of work once you quit.