योगवासिष्ठः yogavāsiṣṭhaḥ - book-6, chapter-6, verse-35

इदं दुर्दुःखमज्ञस्य न कदाचन शाम्यति ।
अनात्मनि शठे देहे आत्मभावमुपेयुषि ॥ ३५ ॥

idaṃ durduḥkhamajñasya na kadācana śāmyati ,
anātmani śaṭhe dehe ātmabhāvamupeyuṣi 35

35. idam durduḥkham ajñasya na kadācana śāmyati
anātmani śaṭhe dehe ātmabhāvam upeyuṣi

35. ajñasya anātmani śaṭhe dehe ātmabhāvam
upeyuṣi idam durduḥkham kadācana na śāmyati

35. This terrible suffering of the ignorant person never ceases, because they identify with (lit. "have attained the sense of self in") the deceitful body, which is not the true self (ātman).

Words meanings summery:

• इदम् (idam) - this

• दुर्दुःखम् (durduḥkham) - great suffering, intense misery, terrible pain

• अज्ञस्य (ajñasya) - of the ignorant, of the unwise

• न (na) - not, no

• कदाचन (kadācana) - ever, at any time, never (with 'na')

• शाम्यति (śāmyati) - ceases, becomes calm, is pacified, is extinguished

• अनात्मनि (anātmani) - in the non-self, in that which is not the self (ātman)

• शठे (śaṭhe) - in the deceitful, in the tricky, in the villainous

• देहे (dehe) - in the body

• आत्मभावम् (ātmabhāvam) - the sense of self, self-identity, belief in self

• उपेयुषि (upeyuṣi) - having attained, having approached, having obtained

Words meanings and morphology

इदम् (idam) - this

(pronoun)

Nominative, neuter, singular of idam

idam - this, this here

दुर्दुःखम् (durduḥkham) - great suffering, intense misery, terrible pain

(noun)

Nominative, neuter, singular of durduḥkha

durduḥkha - great suffering, intense misery, terrible pain

Compound type : tatpurusha (dur+duḥkha)

• dur – bad, difficult, ill
  indeclinable
  prefix indicating difficulty or badness
• duḥkha – suffering, pain, misery, sorrow
  noun (neuter)

अज्ञस्य (ajñasya) - of the ignorant, of the unwise

(adjective)

Genitive, masculine, singular of ajña

ajña - ignorant, unwise, foolish

negated jña (knowing)

Compound type : nañ-tatpuruṣa (a+jña)

• a – not, non-, un-
  indeclinable
  negative particle
• jña – knowing, wise, intelligent
  adjective (masculine)
  from root jñā (to know)
  Root: jñā (class 9)

Note: Acts as a noun here, 'of the ignorant one'.

न (na) - not, no

(indeclinable)

negative particle

कदाचन (kadācana) - ever, at any time, never (with 'na')

(indeclinable)

formed from kadā (when) + cana (particle)

शाम्यति (śāmyati) - ceases, becomes calm, is pacified, is extinguished

(verb)

3rd person , singular, active, present (laṭ) of śam

Root: śam (class 4)

अनात्मनि (anātmani) - in the non-self, in that which is not the self (ātman)

(noun)

Locative, masculine, singular of anātman

anātman - not the self, non-self

negated ātman

Compound type : nañ-tatpuruṣa (an+ātman)

• an – not, non-
  indeclinable
  negative particle, used before vowels
• ātman – self, soul, spirit, essence
  noun (masculine)

Note: Refers to the body, which is not the true self (ātman).

शठे (śaṭhe) - in the deceitful, in the tricky, in the villainous

(adjective)

Locative, masculine, singular of śaṭha

śaṭha - deceitful, crafty, cunning, villainous

Note: Qualifies dehe.

देहे (dehe) - in the body

(noun)

Locative, masculine, singular of deha

deha - body, corporeal frame

Note: The object of the identification.

आत्मभावम् (ātmabhāvam) - the sense of self, self-identity, belief in self

(noun)

Accusative, masculine, singular of ātmabhāva

ātmabhāva - sense of self, self-identity, belief in self, intrinsic nature

Compound type : tatpurusha (ātman+bhāva)

• ātman – self, soul, spirit, essence
  noun (masculine)
• bhāva – state of being, nature, existence, feeling, sentiment
  noun (masculine)
  Root: bhū (class 1)

Note: Object of upeyuṣi.

उपेयुषि (upeyuṣi) - having attained, having approached, having obtained

(adjective)

Locative, masculine, singular of upeta

upeta - approached, attained, endowed with

Past Active Participle

upa + √i + kvasu (participle suffix)

Prefix: upa

Root: i (class 2)

Note: This participle modifies an implied agent (the ignorant person) and agrees in case and number with dehe and anātmani due to being an action performed in that state/object.