I've relapsed on a daily basis for a long time (waking up in the morning vowing NOT to drink at least for one day - ha.) I've relapsed on day one, two, three, four, five, etc and etc.
You're hardly alone, we are alcoholics and we relapse. Identify triggers, dust yourself off and don't drink today.
Willpower alone probably won't be enough for you; it isn't for most people. You need one or more of the following: a plan, IRL support, fellowship, alternate activities, etc.