There is nothing wrong with occasionally having a social drink, but if you are drinking excessively, there are many detrimental side effects for your body. Alcohol consumption in excessive amounts may actually be countering your workouts and rendering them useless. Alcohol is not only bad for brain cells and other living cells in the body as I'm sure you already know, but it can also completely mess up the many benefits you hope to gain from your training efforts.
Alcohol is a natural diuretic which means that it robs the cells in your body of water. Water is necessary to rebuild and gain muscle as well as maintain your metabolism (just mild dehydration can slow metabolism by up to 30%). When you are dehydrated the muscles cannot repair themselves, nor do you have the energy to push them to the intensity necessary for muscle growth and physical progression. Alcohol also has a depressive nature which means that when you consume it, it depresses the bodily systems, making it feel sluggish and causes it to operate more slowly. This effectively slows down your metabolism further, making it more difficult to maintain, or to lose weight. Overtime, it can slow it down significantly enough to actually make you start gaining weight. Worst of all, in an effort to uptake the water lost at the cellular level, the body begins to hold onto more water which results in water retention and puffiness.
If you are currently trying to lose weight, I strongly recommend reducing your alcohol consumption (not cutting it out entirely), and only having a drink or 2 on those social occasions that really call for it.*Disclaimer: Individual results vary based on agreed goals. Click here for details.