I believe the number one killer of sobriety is complacency.
Sobriety is not merely abstinence but building a better life where drinking isn't even a consideration. Personally speaking my recovery plan consists of short and long term holistic goals. Physical, mental, emotional, spiritual, and financial goals. Working towards my goals occupies my time in a positive and productive way so I'm not tempted to drink. Achieving my goals and creating a life better than I could imagine before is positive reinforcement to remain sober.
When one is complacent with recovery is when the mental gymnastics begins. That comes from being arrogant and thinking you've got it under control or being lazy and not wanting to put the work in.