SB 11.20.23

nirviṇṇasya viraktasya
 puruṣasyokta-vedinaḥ
manas tyajati daurātmyaṁ
 cintitasyānucintayā
Synonyms: 
nirviṇṇasya — of one who is disgusted with the illusory nature of the material world; viraktasya — and who is therefore detached; puruṣasya — of such a person; ukta-vedinaḥ — who is guided by the instructions of his spiritual master; manaḥ — the mind; tyajati — gives up; daurātmyam — the false identification with the material body and mind; cintitasya — of that which is contemplated; anucintayā — by constant analysis.
Translation: 
When a person is disgusted with the temporary, illusory nature of this world and is thus detached from it, his mind, guided by the instructions of his spiritual master, considers again and again the nature of this world and eventually gives up the false identification with matter.
Purport: 

Although it is difficult to control the mind, by constant practice the mind can be spiritualized in Kṛṣṇa consciousness. A sincere disciple constantly remembers the instructions of his spiritual master and thereby faces again and again the stark truth that the material world is not the ultimate reality. By detachment and perseverance the mind gradually gives up its propensity toward sense gratification; thus illusion loses its grip on a sincere Kṛṣṇa conscious devotee. Gradually the purified mind completely gives up the false identification with this world and transfers its attention to the spiritual platform. Then one is considered to be perfect in the yoga system.