Bhagwad Gita
Chapter 18, Verse 10
न द्वेष्ट्यकुशलं कर्म कुशले नानुषज्जते।त्यागी सत्त्वसमाविष्टो मेधावी छिन्नसंशयः।।18.10।।
Those who are in a good state of mind do not dislike doing bad work or get too attached to good work. They are sure about what needs to be done.