I just got lazy at around 6 months, started taking sobriety for granted and slipped around 7 months. Didn't slip again for another 6 weeks after that so I told myself it was no big deal and I could do it a few times a year with no worries. It's gotten incrementally worse and I know where it could eventually head back to, I just can't have it in my life at all is the truth of it.
I would say taking sobriety for granted and getting lazy about it cost me.