Bhagavad Gita · Chapter 2: The Path of Understanding

Bhagavad Gita 2.57

yaḥ sarvatrānabhisnehastattatprāpya śubhāśubham | nābhinandati na dveṣṭi tasya prajñā pratiṣṭhitā ||

One who is without attachment in every situation, and who neither rejoices at good fortune nor resents bad: that person's wisdom is firmly established.

Modern context

Neither elated by good fortune nor embittered by bad. This is not coldness; such a person can be warm and fully present. It is freedom from the habit of grading every event as 'for me' or 'against me'. That grading is what turns ordinary life into a constant emotional swing.