I recommend trying some yoga breathing exercises. There are a lot of these that you can do that will help to increase lung capacity and help you to practice breathing fully. You can also download ios or android apps that will train you to pace your breathing.
If anyone born tough and maintain his/her health within design limits then need not worry of Lungs.One should leave smoking habits and Alcohol consumption. First make sure that by regulating and controlling, health disorder can be contained then go for physical exercise such as Yoga ,jogging.
The lungs regenerate themselves so that after a period of years, the lungs of a smoker will be nearly the same as a non-smoker. The best way to build lung capacity is through some sort of aerobic exercise such as walking or swimming. Not all lung disease is reversible, but you can optimize your lung capacity with regular, mild aerobic exercise. Check with your physician before embarking on any new exercise program.