Classical Vedanta · part of the Mahabharata
Bhagavad Gita 2.48
Equanimity in success and failure is itself yoga
योगस्थः कुरु कर्माणि सङ्गं त्यक्त्वा धनञ्जय। सिद्ध्यसिद्ध्योः समो भूत्वा समत्वं योग उच्यते॥
Perform action, O Arjuna, being steadfast in yoga, abandoning attachment, and balanced in success and failure. Such equanimity is called yoga.
What this verse points to
This is the verse that gives the word "yoga" its working definition in the Gita: not a posture and not a technique, but the evenness you keep while the result is still unknown. Krishna is not telling Arjuna to stop caring about the outcome. He is telling him to stop letting the outcome decide what kind of person he is that day.
Note the order. Act first, and abandon attachment inside the acting — not before it as a precondition, and not afterwards as consolation. The equanimity is meant to be found in the middle of effort, which is the only place it can actually be tested.
Sit with it
Bring one unresolved outcome to mind at the start of your sit. Keep breathing evenly while you hold it, and notice where the body tightens when you imagine it going badly.
About the Bhagavad Gita
The Bhagavad Gita is a 700-verse dialogue set on the battlefield of Kurukshetra, in which Krishna counsels the warrior Arjuna at the moment he refuses to fight. Across eighteen chapters it draws together the paths of action, devotion, and knowledge into a single teaching on how to act without being bound by action. It sits inside the Bhishma Parva of the Mahabharata and has been the most widely commented-upon text in the Vedantic tradition, from Shankara onward.
References to this text are given as chapter.verse — here, 2.48.