My wake up call was meeting with an old internet friend from years ago before I started drinking so heavily. The history I had with her made me take a long hard look at how far I'd gone downhill since I started drinking. I looked at how much better she was doing in her own life in 6 years, and how much more poorly I was doing in mine, coupled with the fact that I made an ass out of myself to her several times while I was drunk.
There wasn't anything catastrophically negative that happened to me though, thank god. I didn't have to hit any "rock bottom" so to speak, unless the noticeable decline in my mental function could be considered that. Hopefully I don't need any shocking event like that. Just gotta keep taking it one day at a time.