One must seek the association of persons who are Krsna conscious and who engage in devotional service. Without such association one cannot make advancement. Without such association one cannot make advancement. Simply by theoretical knowledge or study one cannot make any appreciable advancement. One must give up the association of materialistic persons and seek the association of devotees because without the association of devotees one cannot understand the activities of the Lord.

Srila Prabhupada, Srimad Bhagavatam 3.25.25 purport