That by which a fool does not give up sleep, fear, grief, Despondency, and arrogance as well, that resolve (dhṛti), O son of Pritha (Pārtha), is of darkness (tāmasī).
When a fool cannot escape dreaming, fear, grief, depression, and intoxication, courage is darkly inert.
(35) [The constancy] by which a fool will not let go sleep, fear, or grief, depression or exaltation, is constancy in Darkness' way.
18.35 That firmness is considered [Some editions read partha in place of mata (considered).-Tr.] to be born of tamas due to which a person with a corrupt intellect does not give up sleep, fear, sorrow, despondency as also sensuality.
18.35 That Dhṛti by which a foolish person does not give up sleep, fear, grief, depression and passion, O Arjuna, is of the nature of Tamas.
18.35 That, by which a stupid man does not abandon sleep, fear, grief, despair and also conceit -- that firmness, O Arjuna, is Tamasic.