What I can tell you is that yoga is about removing the muck by shining the light of awareness on it. That is why yoga is so hard. None of us wants to look at the muck but looking at is the only way to dissolve it. Thus, there are many times that a yogi may feel filled with darkness. It’s not that the darkness arrived because of yoga, it is that yoga made you aware of all things that were holding you back. The good news is that with this awareness, you have the opportunity to dissolve the muck once and for all. However great the doubt, however deep the despair, you can take comfort in knowing that you are feeling these things because your yoga is doing exactly what it was designed to do. You can also take refuge in the knowledge that whatever you are feeling—whether high or low, will pass, because it always does.