Hi Mia:
This happened to me many times before I managed to quit for good. When you get back on the horse it doesn't mean going back to Day 1. It means, as many have said, a learning experience. Continue with your plan, modify it and upgrade it as necessary and focus on realizing that if you have even one drink it is a battle with alcohol that you cannot win without complete sobriety. Everything else pales by comparison, former friends, etc. Alcohol offers or rather guarantees painful death and, pending that, progressive unhappiness, loneliness. Good luck and every good wish.
W.