Ashtanga Yoga is a beautiful practice. One of the great things about it, is the way it can transform our body. When you start, many things can be quite challenging but after a few years of practice, the same things are very manageable, maybe even easy. Year by year the limits are being pushed further and after a longer period of practice, like a decade or something, you are a totally new person. Guruji's words "practice and all is coming" describe this very well.
In this video Grete Allik is doing some of the more advanced backbends. Beginners, don't worry, you don't have to do these in the near future. :)