Bhagavad Gita 18.35
And that which clings perversely to false idealism, fear, grief, despair, and vanity is the product of ignorance.
यया स्वप्नं भयं शोकं विषादं मदमेव च।न विमुञ्चति दुर्मेधा धृतिः सा पार्थ तामसी॥yayā svapnaṃ bhayaṃ śokaṃ viṣādaṃ madameva ca|na vimuñcati durmedhā dhṛtiḥ sā pārtha tāmasī||
English translation (above): Shri Purohit Swami (1935), public domain. Sanskrit text via github.com/gita/gita (Unlicense).