I have had an advanced yoga practice for many years. I artistically have built Bakasana (Crow Pose), Eka Pada Koundinyasa and chin stand into my daily Surya Namaskar (sun salutation) home practice. Yet the pose that continues to be hard, even after praciticing yoga for fifteen years, is sitting in Half Lotus Pose for 15 minutes as a part of my daily meditation practice.
It's not the most awe inspiring pose to look at but I encourage you to try it. This week make the commitment to sit in Half Lotus or Easy Cross Legged Pose for five minutes everyday. Once the week is over try adding two additional minutes, building up to a 10-15 minute meditation practice. It will put your vinyasa flow practice into perspective and allow you a greater sense of calm in both your mind and body.