The one thing that matters more than what happened
In addiction research there's an important difference between a lapse, a single slip, and a relapse, a full return to old patterns. A lapse makes a relapse more likely, but it does not make it certain, the two are not the same thing.
What actually decides which one you're in has a name: the abstinence violation effect. It's the wave of shame and self-judgment that shows up right after a slip, "I've already ruined it, so what's the point now." That reaction, not the slip itself, is what research identifies as the real mechanism that turns one drink into a full relapse. Which means the most useful thing you can do right now is notice that voice and not believe everything it's telling you.
Source: Relapse Prevention, Marlatt's Cognitive-Behavioral Model, PMC ↗ · Abstinence Violation Effect, ScienceDirect ↗