As mentioned before, Yoga is a way of life. Similarly Yoga should become a part of your lifestyle. After all, it is the only form of exercise which gives you all the benefits which any other form of exercise may give besides increasing your immunity towards any diseases. Usually the trend is you do some kind of exercise during your youth, when you are anyway strong and enthusiastic. But after the age of 35-40 is the real time when you need some sort of exercise.
Yoga is different from all other forms of exercises in many ways.
The very basic difference is that after doing all other kinds of exercises you tend to get tired. Whereas in Yoga, since it is non-competitive there is no stress or mental strain, thus you don't tire after a Yoga session. Most of the exercises tend to have effect on the outer beauty or the physical being, while Yoga also deals with one's spiritual front. Other form of exercises affects the muscular toning of the body only, but Yoga poses are fixed in such a manner that they have effects on internal body organs and glands besides the muscles and the relaxing methods in Yoga soothe the heart, helps to keep the head cool and emphasizes on improving the digestive system. Definitely, But that does not mean you should not do any other exercises.