This is the last flight you ever have to get feeling this horrible, Sobreia.
Don't think of last night as a failure. It's only a failure if you don't get back up, which you have and are doing. Own those 6 good days of sobriety you had. They still happened. No one and nothing can those away from you. Here's to the start of your new life!
And have a good time wherever you're going. I'm well jealous that you're escaping cold, gloomy London!