The point at which you make the decision to drink is not a large piece of time; a month's successful sobriety might depend on a half-hour's time of decision-making. The difference between success and failure usually boils down to a fifteen-minute period (or much less), in which you either make the right call (and keep on swimming) or make the wrong call (and sink the boat).
Thus, it doesn't necessarily take a ton of effort or never-ending diligence through every minute of every day, but it does require that you start making the right call every time that one of "those moments" comes up. One slip sinks the ship and puts you back at square one. The good news is that it gets easier and easier to make the right call, the more you are making the right call to begin with. But none of that is going to work in your favor if you are making the wrong call regularly.
I found that my "reasons" for drinking were not myriad or varied -- there were just a few that kept dragging me down. Each time I'd relapse I'd try to figure out what triggered me, and make damn sure that didn't get me again. If you manage to reliably and consistently short-circuit your five classes of big trigger moments, you are in a much stronger position. It's easier to make strides once you stop repeatedly shooting yourself in the foot.