Bhagwad Gita - Post 178

Verse 19

When the seer beholds no agent other than the Gunas, knowing that which is higher than them, he attains to My Being.

Verse 20

The embodied one, having crossed beyond these three Gunas out of which the body is evolved, is freed from birth, death, decay and pain, and attains to immortality.

Swami prescribes step by step process to transcend the three gunas.

Swami says, 

“Man must use first his Rajo Guna to overwhelm his tamasic tendencies. In this way, dull and negative tendencies are first flushed out and replaced with dynamism.  However, Dynamism too could be dangerous, as it promotes aggressiveness. Hence the next stage is to use the Sattva Guna to ease out the Rajasic tendencies.”

For actual liberation, one must go even beyond the Sattva Guna. 

Swami explains beautifully,

“The three Gunas are bonds, man is bound by them, like a cow whose forelegs are tied together, whose hind legs are bound and whose neck and horns are bound by a third bond. How can the poor Cow move freely when it is bound so?

The Sattva Guna is a golden rope, Rajo Guna is a copper rope and the Tamo Guna an iron rope. All the three bind, in spite of the difference in the cost/ quality of the material with which they bind.  All Bonds are obstacle to freedom”

(From the book- Message of the Lord)

To conclude, Gunas originate from Prakriti and are therefore confined exclusively to the body, mind and intellect. 

Even a most Sattvic person is still bound to this world because, that Sattvic nature is also a Guna, associated with Body, Mind and Intellect which makes him feel, "I am noble, I am Sattvic, I do not hurt others, I do good, see good, I am spiritually advanced, I have known Brahman" etc. 

Whereas, for one to attain realization, one has to transcend all the above which has trace of Avidya or ignorance.

From all the above assertions, all that follow the assertion "I am" must leave (I am happy, I am sad, etc), so that one is left with the inward realization that "I AM" or "SOHAM".

Hence, man should transcend the Gunas and transform himself into a divine being. He should undergo a spiritual metamorphosis, as it were. The Spiritualization and divinisation of man is the ultimate goal of this sacred Bhagwad Gita.

What are the insignia of a person who has transcended the three gunas? Arjuna puts a question: “How can we recognize a person who has transcended the three gunas? What are his qualities? How does he behave?” 

Here, in the next verses is found the gunatita lakshana, which is almost similar to the qualities described as sthitaprajna lakshana in the Second Chapter.

Love.