Bhagavad Gita: Chapter 6/Verse 25

शनैः शनैरुपरमेद्‌बुद्ध्या धृतिगृहीतया ।


आत्मसंस्थं मनः कृत्वा न किंचिदपि चिन्तयेत् ॥६- २५॥

śanaiḥ śanairuparamed‌buddhyā dhṛtigṛhītayā ।
ātmasaṃsthaṃ manaḥ kṛtvā na kiṃcidapi cintayet ॥6- 25॥

By wisdom gasped firmly one should cease actions little by little. Also, having employed the mind tamed within the self, it should cause one not to think of anything. 

śanais śanais (adverb) (indeclinable) = little by little

uparamet (optative, 3rd person, singular) = one should cease actions

buddhyā (feminine, instrumental, singular) = by wisdom

dhṛtigṛhītayā (dhṛti + gṛhītayā) (past passive participle, feminine, instrumental, singular) =  grasped firmly 

ātmasaṃstham (ātma + saṃstham) (adjective, neuter, accusative, singular) = tamed within the self

manas (neuter, accusative, singular) = mind

kṛtvā (gerund) (indeclinable) = having employed

na (adverb) (indeclinable) = not

kiṃcid (adverb) (indeclinable) = anything

api (adverb) (indeclinable) = also

cintayet (causative optative, 3rd person, singular) = it should cause one to think