Thanks @Crunchymum
Feeling crappy this evening..throat is v sore and I feel a bit out of it 
I know exactly how you feel about your night out. I felt the same weekend just gone, and was umming and ahhing about whether I was going to drink right up until the night. I'd kind of decided to give wine/prosecco a swerve as I have no off switch there, but thought I may have a g+t
When OH went to the bar and said 'do you want a G+T?' I actually genuinely didn't fancy one after all and had a diet coke.
Maybe it was the Covid brewing but I didn't fancy drinking or staying too late. I had a good time and it was nice to see friends, but was happy to get home at a reasonable hour!
Try to put it out of your mind until the day, and y'know if you don't fancy going..don't!
If you do, then be kind to yourself and give yourself 'permission' to do what you want to at the time. You may find that you don't actually fancy a drink, or you may find you do, but just have a couple..maybe plan to have a soft drink in between any alcoholic one?
Try not to plan in advance as it just stresses you out and means you start to dread going rather than look forward to it. 