Working out and drinking: Is it a wasted session?

I hit the gym three times a week, religiously knocking back my protein shake after every session, staying on top of my nutrition, and all that. But here’s the catch—every Saturday when I head out, I tend to indulge in a few drinks. It got me thinking: does that habit actually mess with my muscle mass or slow down my gains?
Thanks

Here—take a look...

http://forum.teretana.net/viewtopic.php?t=4756&start=0

http://forum.teretana.net/viewtopic.php?t=743&start=0

http://forum.teretana.net/viewtopic.php?t=1269&start=0

http://forum.teretana.net/viewtopic.php?t=5607&start=0

Anyway, everything you'll need: http://forum.teretana.net 😉