SG, I absolutely have days where I am exhausted for no reason (slept well the night before, etc). Two nights ago I got home from work at took a nap at 7:30, something I never did before recovery. I honestly do think it's caused by our bodies recovering. I've read that PAWS symptoms can last up to two years; that's how long it can take to repair the decades of abuse and poisoning.
My advice is to rest when you feel like you need it (today!) and you will feel better tomorrow. And like Cauliflower said, eating well and exercising daily help as well.
OMD, I hope the business meeting goes well. I'm sorry that drinking is so engrained in the business you are in. I do think that men have a disadvantage when it comes to business and drinking compared to women: men are expected to "man up" and not give excuses while it is more acceptable for women to not drink or have just one. (I know this isn't true in all cases but it seems to be society's expectation of men). I feel for you OMD!