There are a multitude of reasons why we fall into sleep or a kind of dreaminess or even a sense of "nothingness" during meditation, and it's helpful to know what these are so that we can use our practice to work with these states, and discover more clarity, energy, and wakefulness - not only in our practice, but in our daily lives. Shell explores these and more in this talk on what is called the hindrance of "sloth & torpor."