Bhagavad Gita, Chapter 18, Verse 35

That by which a stupid man does not give up sleep, fear, grief, despondency and also overweening conceit, that fortitude, O Pârtha, is Tâmasika.

Real stubbornness is described here as clinging to fear and grief specifically, not letting go even when it clearly should.

Krishna names exactly what's held onto, dreaming, despair, conceit, rather than describing this resolve vaguely. Real refusal to release harmful patterns marks this lowest kind of determination.