In this material world, every materialist desires to achieve happiness and diminish his distress, and therefore he acts accordingly. Actually, however, one is happy as long as one does not endeavor for happiness; as soon as one begins his activities for happiness, his conditions of distress begin.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
सुखाय दुःखमोक्षाय सङ्कल्प इह कर्मिणः । सदाऽऽप्नोतीहया दुःखमनीहायाः सुखावृतः
sukhāya duḥkhamokṣāya saṅkalpa iha karmiṇaḥ | sadā''pnotīhayā duḥkhamanīhāyāḥ sukhāvṛtaḥ
SB 7.7.42