योगवासिष्ठः yogavāsiṣṭhaḥ - book-1, chapter-20, verse-12

इषुप्रपातमात्रं हि सुखदं दुःखभासुरम् ।
दाहपोषप्रदं नित्यं यौवनं मे न रोचते ॥ १२ ॥

iṣuprapātamātraṃ hi sukhadaṃ duḥkhabhāsuram ,
dāhapoṣapradaṃ nityaṃ yauvanaṃ me na rocate 12

12. iṣu-prapāta-mātram hi sukha-dam duḥkha-bhāsuram
dāha-poṣa-pradam nityam yauvanam me na rocate

12. hi yauvanam iṣu-prapāta-mātram sukha-dam
duḥkha-bhāsuram dāha-poṣa-pradam nityam me na rocate

12. Indeed, youth (yauvana) is as fleeting as an arrow's fall, superficially pleasant but radiant with suffering. It constantly causes torment and fosters detrimental growth. This youth (yauvana) does not appeal to me.

Words meanings summery:

• इषु-प्रपात-मात्रम् (iṣu-prapāta-mātram) - merely an arrow's fall; momentary; fleeting

• हि (hi) - indeed; surely; because

• सुख-दम् (sukha-dam) - pleasure-giving; pleasant

• दुःख-भासुरम् (duḥkha-bhāsuram) - radiant with suffering; full of sorrow; intrinsically painful

• दाह-पोष-प्रदम् (dāha-poṣa-pradam) - causing torment and fostering detrimental growth; giving burning and increase

• नित्यम् (nityam) - always; constantly; eternally

• यौवनम् (yauvanam) - the state of being young, personified or generalized (youth; youthfulness)

• मे (me) - to me; for me

• न (na) - not; no

• रोचते (rocate) - pleases; shines; appears good

Words meanings and morphology

इषु-प्रपात-मात्रम् (iṣu-prapāta-mātram) - merely an arrow's fall; momentary; fleeting

(adjective)

Nominative, neuter, singular of iṣu-prapāta-mātra

iṣu-prapāta-mātra - merely an arrow's fall; momentary; fleeting

Compound type : tatpuruṣa (iṣu+prapāta+mātra)

• iṣu – arrow
  noun (masculine)
• prapāta – fall; flight; reach
  noun (masculine)
  From pra- √pat
  Prefix: pra
  Root: pat (class 1)
• mātra – measure; extent; only; merely
  adjective (neuter)

Note: Referring to yauvanam.

हि (hi) - indeed; surely; because

(indeclinable)

Note: Emphatic particle.

सुख-दम् (sukha-dam) - pleasure-giving; pleasant

(adjective)

Nominative, neuter, singular of sukha-da

sukha-da - giving happiness; pleasant; causing joy

From sukha + √dā (to give) with suffix -a.

Compound type : tatpuruṣa (sukha+da)

• sukha – happiness; pleasure
  noun (neuter)
• da – giving; bestowing
  adjective (neuter)
  Suffix from √dā (to give)
  Root: dā (class 3)

Note: Referring to yauvanam.

दुःख-भासुरम् (duḥkha-bhāsuram) - radiant with suffering; full of sorrow; intrinsically painful

(adjective)

Nominative, neuter, singular of duḥkha-bhāsura

duḥkha-bhāsura - shining with sorrow; resplendent with misery

From duḥkha (suffering) and bhāsura (shining, splendid).

Compound type : tatpuruṣa (duḥkha+bhāsura)

• duḥkha – suffering; misery; pain
  noun (neuter)
• bhāsura – shining; radiant; splendid
  adjective (neuter)
  From √bhās (to shine)
  Root: bhās (class 1)

Note: Referring to yauvanam.

दाह-पोष-प्रदम् (dāha-poṣa-pradam) - causing torment and fostering detrimental growth; giving burning and increase

(adjective)

Nominative, neuter, singular of dāha-poṣa-prada

dāha-poṣa-prada - providing burning and nourishment/growth; causing distress and fostering increase (of negative qualities/effects)

From dāha (burning/torment) + poṣa (nourishment/growth) + prada (giving).

Compound type : dvandva (dāha+poṣa+prada)

• dāha – burning; torment; inflammation
  noun (masculine)
  From √dah (to burn)
  Root: dah (class 1)
• poṣa – nourishment; growth; fostering; increase
  noun (masculine)
  From √puṣ (to nourish, thrive)
  Root: puṣ (class 4)
• prada – giving; bestowing; causing
  adjective (neuter)
  Suffix from pra- √dā (to give)
  Prefix: pra
  Root: dā (class 3)

Note: Referring to yauvanam.

नित्यम् (nityam) - always; constantly; eternally

(adjective)

Nominative, neuter, singular of nitya

nitya - constant; eternal; perpetual; always

Note: Adverbial usage here, modifying the effect of dāha-poṣa-pradam.

यौवनम् (yauvanam) - the state of being young, personified or generalized (youth; youthfulness)

(noun)

Nominative, neuter, singular of yauvana

yauvana - youth; youthfulness; prime of life

Derivative of yuvan (young)

Note: Subject of the sentence.

मे (me) - to me; for me

(pronoun)

Dative, singular of asmad

asmad - I; me

First person pronoun

Note: Dative case with rocate.

न (na) - not; no

(indeclinable)

Note: Negating particle.

रोचते (rocate) - pleases; shines; appears good

(verb)

3rd person , singular, middle, present indicative (laṭ) of ruc

Root: ruc (class 1)

Note: The subject (yauvanam) is neuter singular, hence 3rd person singular verb.