Matty, you did the research and now you know what a relapse feels like. Use that information going forward to stop in the future.
None of us are perfect and things like this happen. Don't beat yourself up, use the info.
You're miffed as to why you did it but it takes one fleeting moment of the scales of sobriety vs drinking to tip.
Write this down and stick it in your wallet. The next time that you get into the same position pull it out and read it.
If you're thinking of drinking again, all I can say is: you do NOT want to be in my position now. Drinking is absolutely pathetic and I feel pathetic for having par taken in it again..
Don't lament over it, learn from it, you can do this!