Bg 8.15

mām upetya punar janma
duḥkhālayam aśāśvatam
nāpnuvanti mahātmānaḥ
saṁsiddhiṁ paramāṁ gatāḥ
Word for word: 
mām — Me; upetya — achieving; punaḥ — again; janma — birth; duḥkha-ālayam — place of miseries; aśāśvatam — temporary; na — never; āpnuvanti — attain; mahā-ātmānaḥ — the great souls; saṁsiddhim — perfection; paramām — ultimate; gatāḥ — having achieved.
Translation: 
After attaining Me, the great souls, who are yogīs in devotion, never return to this temporary world, which is full of miseries, because they have attained the highest perfection.
Purport: 

Since this temporary material world is full of the miseries of birth, old age, disease and death, naturally he who achieves the highest perfection and attains the supreme planet, Kṛṣṇaloka, Goloka Vṛndāvana, does not wish to return. The supreme planet is described in Vedic literature as avyakta and akṣara and paramā gati; in other words, that planet is beyond our material vision, and it is inexplicable, but it is the highest goal, the destination for the mahātmās (great souls). The mahātmās receive transcendental messages from the realized devotees and thus gradually develop devotional service in Kṛṣṇa consciousness and become so absorbed in transcendental service that they no longer desire elevation to any of the material planets, nor do they even want to be transferred to any spiritual planet. They only want Kṛṣṇa and Kṛṣṇa’s association, and nothing else. That is the highest perfection of life. This verse specifically mentions the personalist devotees of the Supreme Lord, Kṛṣṇa. These devotees in Kṛṣṇa consciousness achieve the highest perfection of life. In other words, they are the supreme souls.