This is a great topic, whether it's called a relapse or just plain drinking again, when we know better.
For me, there are a variety of situations/people/emotions that cause my brain to go right down that path. They are varied, and some are easily avoidable. Some are unavoidable- just daily situations (tired after work, Friday evening at home, no kids at home, cleaning), it's just a matter of using the strategies that we know work for us individually rather than caving in to that first voice that tells us that drinking would be a great idea right now. I know exactly what my voice tells me when it's trying to convince me to drink. It's predictable. And I have successfully shot it down many times. Why not every time? Because I don't fight for it. Like Nudawns analogy, drinking is the Easy button.