When one's mind is attached to Krsna, one can fulfill the mission of life in one human birth. If one misses this opportunity, one does not know where he is going, how long he will remain in the cycle of birth and death, and when he will achieve the human form of life and the chance to return home, back to Godhead. The most intelligent person, therefore, uses every moment of his life to render loving service to the Lord.
His Divine Grace A.C. Bhaktivedanta Swami Prabhupada
Srimad-Bhagavatam 9.9.42, Purport
Men who do not know the principles of devotional service to the Supreme Lord should be known as cows and asses, even if they are expert in technically analyzing Vedic mantras and are adored by world leaders.
Brhaspati-samhita
The soul's nature is spiritual. In the soul's heart is pure love, love for Krsna alone. Now the soul is covered with lust. Now that original love for Krsna sleeps. Chase the lust far away. Awaken the spiritual love.
Srila Bhaktivinoda Thakura
Kalyana-kalpataru 1.19.2
We have now plunged into the great nectar-ocean of the transcendental youthful pastimes of Maharaja Nanda's son, Krsna. Of what use to us is the saltwater of impersonal liberation.
Sri Yadavendra Puri
Sri Padyavali 42
Strive, strive only for the association of pure devotees of Lord Krsna.
Sri Narada Muni
Narada-bhakti-sutra 42
I regard as great even the smallest gift offered by My devotees in pure love, but even great offerings presented by nondevotees do not please Me.
Lord Sri Krsna
Srimad-Bhagavatam 10.81.3
The Supreme Lord manifested the material intelligence, senses, mind, and vital air of the living entities so that they could indulge their desires for sense gratification, take repeated births to engage in fruitive activities, become elevated in future lives, and ultimately attain liberation.
Sri Sukadeva Gosvami
Srimad-Bhagavatam 10.87.2