Have an innocent glass of wine or a drink - then another (Please not a third libation). All of the sudden your words are slurring, you are throwing your current employer under the bus and the wheels are suddenly coming off. You've let your hair (and your guard) down. You may have forgotten the person’s name across the table from you and who knows what other thoughts might come out of your brain and eventually out of your mouth. This is a recipe for a real disaster. Some people are just wired that way. Two drinks (wine, beer or liquor) and it's (well) game over. Not good.
You are there to prove you are the best person for the job - not to showcase your drinking skills. You want to be remembered as the professional that met the hiring manager for dinner, had a nice conversation and an enjoyable meal. Hopefully your performance will yield an offer the next day or so after showcasing your social skills.
Take the high road every time when it comes to alcohol during any important meeting and you will come out on the right side of the equation. Take the low road and well... you might be calling a cab starting over from scratch on your job search after you sleep off your headache.
Be smart!