[5] Dhruti, meaning 'fortitude' and 'determination', is defined as the subtle faculty in a person that makes them strive continuously towards a goal.
Dhruti is a quality of peace, courage, patience, enthusiasm, and perseverance to face and overcome all odds and obstacles.
The Vedic Rishis address their prayers to the Visvedevas just as they do the Adityas and the Maruts; who all as a group are the protectors of the ten Rtas including Dhrti ('forbearance') which word represents an abstract idea like Hri and Kirti.
[12] As part of the performance of the Ashvamedha yajna, as mentioned in the Shatapatha Brahmana, Asvalayana-srauta-sutra, and Sankhayana-srauta-sutra, the Adhvaryu offered, for the safe movement of the Sacrificial Horse during day-time, three Istis daily to Savitr and at nightfall performed four Dhrti Homas for the safe sheltering of that horse during night-time.
While the Dhrti Homas were in progress, a Rajanya (Kshatriya) lute-player (veenagathi) sang three songs (Gatha) made up of many verses in which he praised the royal-sacrificer with the mention of his heroic exploits, viz., the wars he waged, the battles he won, the conquests he made, so on.
[15] Dhrti meaning 'fortitude' and 'determination' is defined as the subtle faculty in man that makes him strive continuously towards a goal.
[18] The two factors that supply the fuel and the motive force in all sustained endeavours are - buddhi ('understanding') and dhrti ('fortitude'), the former is 'the intellectual capacity to grasp what is happening' and the latter is 'the constancy of purpose and self-application'.
It is the sattavic dhrti which is strength, force and ability that makes us hold on to noble values of life.
Which means the function of the intellect is discrimination, the faculty of 'right understanding ' (buddhi) which gives real joy, success and prosperity.
Discriminatory wisdom as virtue is the cause of happiness, and both, Vyasa and Vijnanabhikshu in their commentaries list nine causes including as the ninth cause Dhrti here meaning sustenance; and agree that the yoga-angas eradicate the impurity in both tangible (drshta) and intangible (adrshta) ways i.e. the physical practices such as purification (shaucha), and through japa.