Vasiṣṭha's teaching (Mahārāmāyaṇa) 3.60.18

3.60.18

yathā bhāvitameteṣāṃ padārthānāṃ nijaṃ vapuḥ .
tadeva hi cirābhyāsānniyatervaśamāyatam .. 18

17. [Sanskrit available] Take for instance the destructive poison, which becomes as ambrosia to venomous insects, that take it for their dainty nourishment; and so is an enemy turning to a friend by your friendly behaviour unto him. (In both cases the evil turns to good by our taking it as such).

18. [Sanskrit available] And the manner in which all beings consider themselves, and all others for a length of time; the same they seem to be by their mode and habit of thinking, as if it were by an act of destiny (i. e., they consider their thoughts of things as their destined nature, which is not so in reality; for fair is foul and foul is fair; according as our judgments declare).