The doubts are part of your beast's nefarious efforts to undermine your own resolve and get you drinking again. You must believe in yourself fully, completely and absolutely. You are not quitting drinking, this is something that has already happened. A completed action in the past.
Doubts in your ability, and thoughts about drinking again are no longer yours but your beast's. Again, this is a certainty because of the implications of your BP.
I don't know about you, but attending a party at the request of some attractive persons of that other sex would be a high risk activity. Be aware and mindful of yourself and your thoughts. They aren't bad per se, but you can make this easier on yourself if you step back a bit and let your awareness go to work for you.