Chapter 12 · The Yoga of Devotion · Krishna said
Bhagavad Gita 12.12 — Peace through letting go
श्रेयो हि ज्ञानमभ्यासाज्ज्ञानाद्ध्यानं विशिष्यते। ध्यानात्कर्मफलत्यागस्त्यागाच्छान्तिरनन्तरम् ॥
śreyo hi jñānamabhyāsājjñānāddhyānaṃ viśiṣyate | dhyānātkarmaphalatyāgastyāgācchāntiranantaram ||
Meaning
Knowledge is better than mechanical practice, and meditation is better than knowledge. Better than meditation is giving up the fruits of action, for peace follows that letting go at once.
In today's life
Doing your best and then letting go of the outcome is one of the surest ways to inner peace.