Yeah I know the feeling. That is, it's somehow so much harder to bounce back from a relapse that was done in celebration versus one that was done due to stress or some other negative emotion. I think it's because when things are bad it's much easier to justify drinking. "It will relieve the stress, just for tonight, I need this" and it does, for a little while. Then the next morning you feel worse and you think. "Well I was really stressed anyway." Likewise it's sometimes easier to not drink when you are stressed because you have hope. "This sucks now, but if I don't drink at least I'll feel good about that and things will get better."
But drinking due to celebration is a whole nother' monster. Things are good! And you want them to be better? At least for me, drinking never really made things much better temporarily when things were already good. Then the next morning comes and you think. Why??? Things were so good! Now this is terrible..... I felt good, why did I screw it up?
These are sort of illusions. If you make a commitment to yourself to not drink. It doesn't matter why or how, if you break it, you have to start over. It is puzzling why we want to drink when things are both good and bad, but it doesn't really matter why. All that matters is that we don't.