Haha, drinking while brewing is the best/worst idea ever. I hate getting a little buzzed and then doing EVERYTHING in panic mode. Not necessarily doing everything too quickly, but just being unsure of what you're doing because you're not concentrating.
I normally brew with other people around but recently I had to go solo, so I decided not to pound the beers like usual... I drank 4 beers from mash-in to clean up (about 6 hours) and I gotta say, it was a much smoother experience. I made a conscious decision not to drink as much during brewing for future sessions.
Or if you're like me and once you get sipping, there's no stopping, you should just set a time when you're "allowed" to have your first beer.