We live day to day life in stress (mental + physical). This stress keeps our body in flight and fight situation and result is shallow breathing. When this happens years and years, total vital capacity of lungs reduces drastically. Yoga (especially pranayama) teaches us to be aware of breathing and then natural rhythm of breathing sets in. But reverting existing damage takes time.
The more you get yourself involved into yoga (mindfully), the more you find ways to be conscious. Its natural process. At any point of time if you still need alcohol that means you are very far from yoga. There is no point stopping drinking forcefully.