When the seer perceives no agent other than the gunas, and knows what stands beyond the gunas, he attains my own being.
Explanation
Krishna has just described where beings of each guṇa (strand of nature: sattva, rajas, tamas) end up. Now he says that real insight is seeing that all action is carried out by the guṇas, and that the self (the witness) is distinct from them. One who knows this reaches Krishna's own state (madbhāva). Traditions differ on what this state is: Advaita reads it as oneness with the Absolute, while devotional schools read it as sharing in Krishna's divine nature while remaining his devotee.