Mahabharata 12.168.19

सुखात्त्वं दुःखमापन्नः पुनरापत्स्यसे सुखम्न नित्यं लभते दुःखं न नित्यं लभते सुखम्

sukhāttvaṃ duḥkhamāpannaḥ punarāpatsyase sukhamna nityaṃ labhate duḥkhaṃ na nityaṃ labhate sukham

Our plain-language meaning of this verse is waiting for scholar review.