Śrī Prabuddha said: Accepting the roles of male and female in human society, the conditioned souls unite in sexual relationships. Thus they constantly make material endeavors to eliminate their unhappiness and unlimitedly increase their pleasure. But one should see that they inevitably achieve exactly the opposite result. In other words, their happiness inevitably vanishes, and as they grow older their material discomfort increases.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
प्रबुद्ध उवाच । कर्माण्यारभमाणानां दुःखहत्यै सुखाय च । पश्येत्पाकविपर्यासं मिथुनीचारिणां नृणाम्
prabuddha uvāca | karmāṇyārabhamāṇānāṃ duḥkhahatyai sukhāya ca | paśyetpākaviparyāsaṃ mithunīcāriṇāṃ nṛṇām
SB 11.3.18