Contrary to popular misconception, yoga is not only for those who are calm, flexible and strong. While sculpted bodies and enviable serenity may be outcomes of long term yogic practices, one need not have such characteristics to begin with. You can do yoga! Yoga can truly help anyone!
Pattabhi Jois is considered the father of Ashtanga Yoga as it is practiced now. He began learning at the age of 12 from Krishnamacharya, the father of modern yoga.