"My dear Lord, devotional service unto You is the best path for self-realization. If someone gives up that path and engages in the cultivation of knowledge or in speculation, he will simply undergo a troublesome process and will not achieve his desired results. A person who beats an empty husk of wheat cannot get grain, and one who engages simply in speculative knowledge cannot achieve the desired result of self realization. The only gain is trouble."
In Bhagavad-gītā it is stated (BG 7.14) that material nature is so strong that it cannot be surmounted by an ordinary living entity. Only those who surrender unto the lotus feet of Kṛṣṇa can cross the ocean of material existence. The living entity forgets that he is eternally the servitor of Kṛṣṇa, and his forgetfulness causes his bondage in conditional life and his attraction for material energy. Indeed, that attraction is the shackle of material energy.