I became interested in Ayurveda, an Indian medical system which is sometimes called the sister science to yoga, in the early 90’s. I admire practitioners of this ancient discipline, like Gita Iyengar, especially as she so adroitly combines Ayurveda with many yoga practices.
When I came across the notion of gunas in Ayurveda, I learned that these elements of nature provide a system for assessing one’s condition to see if there’s a tendency towards tamas, sattva or rajas. A sattvic nature is deemed to be balanced, ordered, and pure so you might imagine this is a way of being that yogis would want to aspire to.
Patanjali’s Yoga Sutra point us towards cultivating a sattvic disposition with practices that develop a witnessing awareness in meditation so that our thoughts, beliefs and even ego identity are seen to be objects of perception.
How hard is it to foster this level of awareness? For me, very. I’m still working on paying enough attention when I brush my teeth so each separate tooth gets attended to. Sigh.

Drasta drsimatrah suddhah api pratyayanupasyah

The seer is pure consciousness. He witnesses nature without being reliant on it.*

Intelligence, belonging as it does to manifest nature, is constantly changing, sometimes conscious and often unconscious. It is subject to sattva, rajas and tamas, whereas the seer, purusa, is beyond all these, immutable and ever-conscious.*

*Light on the Yoga Sutras of Patanjali, B.K.S. Iyengar.