Samsara, or this phenomenal world, is constituted by Ragas and Dveshas, which literally mean attractions and aversions. They form a part of Pancha-Klesha (The five root causes of suffering). These originate in the mind and senses. Born out of Avidya or ignorance (lack of true knowledge), Ragas and Dveshas can be destroyed only by the knowledge of the self and the supreme (Brahma-Jnana). Else, they become a rope which binds us and brings misery.
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The cravings for pleasure based on sense gratifications of the past is what causes attachment for that object or experience. Similarly aversion towards a particular object, person, or experience creates a similar impression on the mind and causes it to run away or avoid that in the future. WIthout proper knowledge, these mental patterns are born out of a loss of awareness, perspective and objectivity. Basically, it is the focus on the external sources of happiness and misery instead of the self, which is the source of all bliss and joy.
Pleasure and pain, Harsha and Soka, exhilaration and depression are due to Raga-Dvesha. If Raga and Dvesha vanish from the mind, Harsha-Soka also will disappear. – Swami Shivananda
In the second chapter of The Bhagavad Gita, verse 64, we see –
viṣayān indriyaiś caran
“But the disciplined (lower) Self, moving among sense-objects with senses free from attraction and repulsion and mastered by the Higher Self, goeth to Peace.”
Another important aspect of these twin Kleshas (or poisons), is that both are intertwined. One cannot occur without the other, and both are equally harmful to one’s consciousness. For example, if we have attachment to a relative, at the time of death, there is separation and the mind craves for the presence of the person, giving rise to misery. This unfulfilled craving leads to fear, anger and frustration, giving rise to more suffering.
Practice of Yoga and non-attachment (vairagya) is the means to overcome such innate inner tendencies which are carried forward from many lifetimes. The fire of Vairagya burns up these seeds of attachment and aversions. Being non-attached in both pleasure and pain, happiness and sadness, helps one rise above them and become balanced and poised. Regular Yogic practice (sadhana) and meditation on the divine (dhyana) are essential to train the mind and make it calm and equanimous.