The stream of thought: tumbling or lethargic?

During these hot days of June in Central Virginia, I have been walking my dog by the cool stream as often as possible.  I notice how sometimes the water moves in fast, energetic turbulence.  Sometimes it sits in muddy stagnation.  Other times it flows in gentle clearness.

As risk of oversimplification, we can think of the gunas this way.  The fast moving water is like the trait of rajas, which is energetic.  The slow moving water is like the trait of tamas, which is sluggish.  The flowing water is like the trait of sattva, which is clear.

These qualities of nature (the gunas) are the foothold of Samkhya philosophy, and are often referred to in Patanjali's Yoga Sutras.  Patanjali assumed that the student would already know these basic constituents of nature, and builds many of his arguments on this foundation.  If you want to see more, check out:  Book II Sutras18-19 and Book IV Sutras 13-14; 32-34.
 
I see these qualities in students as they arrive at class.  After class, they often report that they have a renewed sense of balance and clarity.  It often comes out like this: "I'm so glad I came, even though I was tired.  Now I have some energy!"  Or, "I was so amped up before class.  Now, I still have energy, but I feel calm at the same time."

Sometimes, during class, I ask students to observe their minds.  Are their thoughts tumbling like the rapids in a stream?  Or is their mind lethargic?  Ideally, by the end of an appropriate asana and pranayama practice, their minds feel clear and flowing.

And what better way to approach life?