RecoveryForMe,
Brush yourself off and try again. We all have fallen, but the main thing is to realize what happened and why. Examine the triggers that lead you to drinking last night. I always do that now and it helps. I asked myself if I am putting myself in danger of drinking in certain situations...and if I answer myself "yes". Then I don't go.
I too was invited to a Halloween party of a family member. I am not comfortable around my family and too fresh in recovery. I would have been anxious and ended up drinking to relieve stress. Sometimes we need to examine what we need to give up in order to achieve sobriety. For me, its social events with alcohol present. I know I won't make it!
Hope this helps.