I wish I'd realized, at the time, that the fatigue which kept me from checking my watch was actually the consequence of not training effectively. This turned out to be equally true of my tunnel vision. As soon as I started training to heart rate, I felt more comfortable. I was listening to my body and working within my limits. I could look at my watch or around the neighborhood, even chat with other runners! For the first time, I was actually able to enjoy myself and experience flow when I was running.
There are multiple layers of complexity within yoga. On the one hand, there are poses that are physically challenging to any yogi. On the other hand, the holding of poses for longer periods of time can be mentally and emotionally challenging. Poses may be physically difficult because they require a great deal of strength, balance, flexibility, or quick movements from pose to pose. The faster a participant moves through a sequence, the more demanding it is.