Good morning lovely Babes. 
This thread has been so busy the last couple of days - there are loads of posts I'd like to respond to but it's all too complicated! 
Huge well done to Soma - you really were a sad Soma when you posted on here a few days ago and you just sound so different now. Like you've found hope and strength. 
Lola said "Feel like my willpower is ebbing away, having a bad week..."
Lola I'm reading a book about willpower at the moment that I've found really useful. It's based on good solid research but I'm just going to re-jig and summarise the bit I thought might help you in a cack-handed way that would probably appall the authors 
Imagine your willpower as a liquid substance, filling up a nice pretty jug. Your jug is filled up with willpower in the morning, and you have to make it last for the day. Every time you apply your willpower to something, you're pouring yourself a glass out of the jug. Each act of self-control depletes the pot, iyswim. Another thing that uses up your willpower is making decisions, particularly stressful decisions. You have to keep taking little swigs from the jug to decide all these umpteen decisions you're having to make every day.
Just to complicate things a little more, your blood sugar levels make a significant difference to how much you drink from the jug. If you're hungry and hypoglycaemic, you'll use a lot more willpower from the jug in order to exert self-control or make decisions. Eating regularly and providing your body with fuel and glucose (preferably complex carbs that release the glucose slowly) means you don't deplete your jug so fast, and can even replenish it a bit.
So the point of this rambling nonsense little story is this; if you want to not drink today (tomorrow, the next day etc), cut yourself some slack on other things - just concentrate your pot of willpower on that not-drinking. Make sure you are eating regularly enough to keep your blood glucose levels up - preferably healthy low-GI stuff, but hey - whatever works.
Try to avoid having to make loads of decisions (or if you do have to, be aware that this will affect your ability to exert self-control). The reason I thought of this is because your post reminded me of how I was feeling on Saturday when I couldn't decide whether to drink in the evening or not. I thought about it, debated it, worried about it, all fucking day.
I was exhausted by the evening (as was poor DP
) and although I didn't drink, I had a crap evening. Sunday night and last night, however, the decision was already made that I wasn't going to drink, I had confidence that I'd stick to it, and it barely troubled me. All of this back-and-forth in your head about what to do is exhausting and will deplete your ability to resist temptation.
I can't make the decision for you, but could you suggest to the others that if you (selflessly, generously
) stay sober to save everyone cab fares, then they can treat you to a lovely evening of drinking never some time in the future? That way you defer your 'treat', they don't question why you're not drinking, you get brownie points for being the driver, and your halo can nicely illuminate how undignified everyone looks when they're really pissed.
Believe me noone will think you're being boring or not the life and soul - they'll be too drunk to notice. 