Bhagavad Gita · Chapter 2: The Path of Understanding
Bhagavad Gita 2.56
दुःखेष्वनुद्विग्नमनाः सुखेषु विगतस्पृहः ।
वीतरागभयक्रोधः स्थितधीर्मुनिरुच्यते ॥
duḥkheṣvanudvignamanāḥ sukheṣu vigataspṛhaḥ | vītarāgabhayakrodhaḥ sthitadhīrmunirucyate ||
One whose mind is not shaken by sorrow, who does not crave pleasure, and who is free from passion, fear, and anger is called a sage of steady mind.
Modern context
Three things unsteady us: craving for what we like, fear of losing it, and anger when it is taken or denied. They are one chain. The steady person still meets sorrow and pleasure like everyone else; the difference is that sorrow does not shake them and pleasure does not leave them hungry for more.