विषयेन्द्रियसंयोगाद्यत्तदग्रेऽमृतोपमम्। परिणामे विषमिव तत्सुखं राजसं स्मृतम् ॥

viṣhayendriya-sanyogād yat tad agre ’mṛitopamam pariṇāme viṣham iva tat sukhaṁ rājasaṁ smṛitam

That which from the union of the senses with their objects at first is as nectar, but in the end is like venom, that pleasure is accounted passionate.

In plain words: Krishna says some pleasure comes from the senses meeting the things they enjoy. It feels sweet at first but turns bitter, like poison, in the end. He calls this the restless, passionate kind of pleasure.