1. Patience or fortitude- The mental ability to overcome the ennui; it is attained by the Kṣayopaśama (destruction-cum-subsidence) of the Arati Moha Karma (a sub-type of the deluding karma responsible for creation of ennui (Arati) in the practice of asceticism).
dhitī tu mohassa uvasame hoti.
(NiBhā 85)
2. Stoicism (ability to endure physical pain or mental anguish)- Psychic healthiness, tenacious unperturbedness.
dhṛtiśca cittasvāsthyamanudvignatvamityarthaḥ.
(U 32.3 ŚāVṛ Pa 622)
3. A quality of the anuyogakṛt (Acārya (preceptor)), by the virtue of which he does not get confused (or go astray) while comprehending the very deep connotations of the canonical texts; he does not become skeptic, and remains free from disbelief.
dhṛtiyuto nātigahaneṣvarthesu bhramamupayāti.
(BṛBhā 241 Vṛ p. 75)