Bhagavad Gita 2.15 · BG 2.15
Chapter 2Verse 15
Sankhya Yoga
यं हि न व्यथयन्त्येते पुरुषं पुरुषर्षभ। समदुःखसुखं धीरं सोऽमृतत्वाय कल्पते॥
yaṁ hi na vyathayanty ete puruṣaṁ puruṣarṣabha, sama-duḥkha-sukhaṁ dhīraṁ so 'mṛtatvāya kalpate
Translation
The person whom these do not trouble, who stays steady in pain and pleasure alike, that wise one is fit for immortality.
Stay level through the good days and the bad ones. That steadiness is what lasts.
What does this mean?
The same events hit everyone. What changes is whether they knock you over. Someone who stays level through both a good day and a bad one isn't suppressing anything. They've just stopped handing their stability over to whatever the day brings.
In simple words
Krishna says the person who isn't knocked over by pain or pleasure, who stays about the same through a good day and a bad one, is the one ready for something lasting. It's not that they've stopped feeling. They've stopped handing their stability to whatever the day brings.
The deeper idea
This continues the previous verse's point about sensations coming and going, and draws the consequence: steadiness through both poles is what makes a person fit for the deathless thing the Gita keeps pointing at. The word for the steady person suggests composure rather than coldness. What's being praised isn't indifference to life. It's no longer being at the mercy of its swings, which is treated as a prerequisite for anything deeper opening up.
How it applies to life
Track your mood against your circumstances for a week and the correlation is usually near total, good news up, bad news down, with almost no space in between where you get to choose your response. This verse points at widening that space. Not so you feel nothing, but so a rough Tuesday doesn't fully own you, and a win doesn't leave you unable to function once it fades.