Bhagavad Gita Verse 11, Chapter 14

sarvasvaareshu dehesminprakaasha upajaayate |
jnyaanam yadaa tadaa vidyaadvivriddham sattvamityuta || 11 ||
 
When luminous knowledge radiates through all gates of this body, then one should know that sattva has increased greatly.
 
sarvasvaareshu : in all gates
dehe : body
asmin : this
prakaashaha : luminous
upajaayate : radiates
jnyaanam : knowledge
yadaa : when
tadaa : then
vidyaat : one should know
vivriddham : increased
sattvam : sattva
iti : this
uta : definitely
 
What are the marks of sattva? Shri Krishna says that when we see radiance, or when we see knowledge radiating from a person, we should know that we are in the presence of a highly sattvic person. The word “dvaara” usually means door or gate, but here it refers to the sense organs, our doors to the world. Even though the sense organs are meant from receiving stimuli from the world, they can also convey our internal state to the world. Our eyes, especially, can give away our thoughts. If our mind is wandering, our eyes will also wander, for instance. In a sattvic person, radiance shines through the sense organs, especially the eyes.
 
Now, we should not think that a highly sattvic person will radiate beams of light from their body. But they do radiate calmness and peace. We can sense peace if we are near them, or pick up on their calmness if we are watching them on a screen. Watch Dr. Jane Goodall speak about her efforts to save gorillas in Africa, and you will be drawn to the serenity on her face instantly. Such people harbour few, if any, selfish desires in their mind. This lack of dirt in the form of selfishness lets their inner radiance, the light of their eternal essence, shine through.
 
From our perspective, whenever we notice an increase in clear thinking, we should know that sattva is predominant in our mind. If we see fried food but the intellect prevents our hand from reaching to pick up that food, we are in a sattvic state. If our thoughts are towards the well-being of the family, our city or our nation, instead of just our narrow well-being, we are in a sattvic state. If our mind is sharp and alert, if we don’t let anything drop in our personal and professional lives, we are in a sattvic state.

Bhagavad Gita Verse 9, Chapter 14

sattvam sukham sanjayati rajaha karmani bhaarata |
jnyaanamaavritya tu tamaha pramaade sanjayatyuta || 9 ||
 
Sattva binds through joy, rajas through action, O Bhaarata, while tamas cloaks knowledge and binds through heedlessness.
 
sattvam : sattva
sukham : joy
sanjayati : binds
rajaha : rajas
karmani : action
bhaarata : O Bhaarata
jnyaanam : knowledge
aavritya : cloaks
tu : while
tamaha : tamas
pramaade : heedlessness
sanjayati : binds
uta : and
 
Shri Krishna recaps the characteristics of the three gunaas in this shloka. Sattva binds by making us hold on to joy experienced after attaining a sense object. Rajas binds us by giving us joy in performing actions and obtaining their results. Tamas binds us by giving us joy in holding on to laziness and heedlessness. We now begin to look into how these three are interrelated.
 
In the second chapter, we have come across a series of shlokas that describe how the mind can fall from sattva into rajas and tamas in a matter of seconds. We start with the mind resting in a peaceful sattvic state. A tinge of rajas comes in, causing us to think about some sense object, let's say a sweet. This fuels rajas further, creating a strong attachment to that sweet, culminating in a strong desire to do anything to get that sweet. But it gets worse. If we cannot get that sweet, if someone or something obstructs our consumption of the sweet, anger arises in us. Rajas deteriorates into tamas. The last rung of the ladder of fall is when anger goes to such an extent that it causes us to lose our faculty of intelligence and memory.
 
Conversely, we can go from tamas to rajas to sattva, but it may take a little longer. For someone steeped in tamas, immersing themself in action will raise them to the level of rajas. When action becomes focused and directed towards the pursuit of a selfless goal, rajas is elevated to the level of sattva. Swami Vivekananda always used to say "awake, arise, stop not till the goal is reached". When India was under British rule, many had become accustomed to this slavery and had fallen into a tamasic state. They could not find a way out of their predicament, and were clouded in ignorance. Swami Vivekananda's message urged citizens to engage in action towards independence. That was the only way to get them out of the tamasic state of laziness.