By ‘Guna‘, we mean quality or virtue. Everyone has qualities in them, this is what defines one’s character. According to the Bhagavad-Gita, there are three Gunas, viz Sattva (Positive and Divine), Rajas (Mixed and Human) and Tamas (Negative and Demonic). We all have these qualities in different compositions. And based on the size or composition of these gunas, our personality is defined. Our behaviour, emotions and attitude towards the world are portrayed the way there are because of these three virtues. The goal of the gunas is to create an attachment to this world. And it is only because of this attachment or bondage, we have worldly desires and this is exactly how Prakriti (Nature) works. Nature itself has given birth to these gunas.
As a human, we need not look outside to search for God. One needs to see his inner self to connect with God. The Almighty resides in us. But sadly, because of Maya (Illusion), we always look outside and are attached to sense objects, which hinder the ability to see within. In the realm of Divine Consciousness, everything is in perfect balance. Creation takes place when the balance is disturbed. And it with creation, one inherits all the three gunas. This is when we lose the abilty to realize truth or seek God. Because all the three gunas in different proportions will never enable us to see God who is seated right in your heart. Hence, we are entangled in this cycle of birth and death.
In the Bhagavad-Gita (14th Chapter), Lord Krishna narrates the definition of all three gunas. Sattva is pure, devoid of any impurity and is a quality of wisdom and intelligence. There is happiness and joy here and the binding force here is stability, clarity and harmony. When the Sattva guna is at peak, the human body radiates divine quality and one can experience the awakening of the soul. Rajas is born out of desires. Where there is attachment, there is passion and this trait is found here. Greed and selfishness is what dominates you and your thirst for worldly desires is never quenched here. Tamas is darkness. This causes decay in man. One is lazy and always indulged in sleep. There is inactivity and downward motion here. Tamas is associated with negativity and delusion.
It is impossible for a human to have only one of these qualities. As said before, the nature has a design and a human will possess all these three gunas. People behave differently based on these three qualities. The Gita does not say that one must eliminate Rajas and Tamas and remain Sattvic. There is no such encouragement. What it says is that, these three gunas, sattva, rajas and tamas are a part of nature that are responsible for our illusions and the sufferings on earth. The aim is to attain liberation from all these three qualities. Even if someone achieves to lead a life with only sattva guna, it does not mean the person has attained moksha (liberation from cycle of birth and death).
The trick is to go beyond all these qualities to free us from the birth of cycle and death, in other words, to become one with the Brahman which is otherwise known as ultimate reality. In the 16th chapter, the Bhagavad-Gita expounds valuable information on how to practice devotion to become a perfect yogi, a person devoid of any attachment. It is difficult to put this into practice. Unless one dedicates his life to attain salvation and disregards materialistic life, it is impossible to attain moksha.