BG 18.34

 Bhagavad Gita (Bhagavad Gita 18.35) in Sanskrit:

यया स्वप्नं भयṁ शोकं विषादं मदमेव च ।
न विमुञ्चति दुर्मेधा धृतिः सा पार्थ तामसी ॥ १८.३५ ॥

Transliteration:

yayā svapnaṁ bhayaṁ śokaṁ viṣādaṁ madam eva ca
na vimuñcati durmedhā dhṛtiḥ sā pārtha tāmasī

English translation:

“O Partha (Arjuna), the determination (dhṛti) by which a person of poor understanding does not give up sleep, fear, grief, despondency, and delusion/pride — that determination is declared to be tamasic (born of inertia and darkness).”

Meaning

In Chapter 18, Krishna explains three kinds of determination (dhṛti) — sattvic, rajasic, and tamasic.

Verse 18.35 describes tamasic determination:

• A person remains attached to sleep/inertia,
• fear,
• sorrow,
• depression/despair (viṣāda),
• and delusion or intoxication with ego (mada),
  and cannot let go of them.

The key idea is that even stubbornness or persistence is not always positive. One can be “determined” in unhealthy mental patterns too.

It contrasts with:

• 18.33 — sattvic determination: steady discipline that supports yoga and self-mastery.
• 18.34 — rajasic determination: persistence driven by desire and attachment to results.
• 18.35 — tamasic determination: clinging to confusion, fear, and inertia.