Srimad-Bhagavatam: Canto 11 - Chapter 1 - Verse 36
विष्टभ्य चित्तं प्रणयावघूर्णंधैर्येण राजन् बहु मन्यमान: ।कृताञ्जलि: प्राह यदुप्रवीरंशीर्ष्णा स्पृशंस्तच्चरणारविन्दम् ॥ ३६ ॥
viṣṭabhya cittaṁ praṇayāvaghūrṇaṁdhairyeṇa rājan bahu-manyamānaḥkṛtāñjaliḥ prāha yadu-pravīraṁśīrṣṇā spṛśaṁs tac-caraṇāravindam
Steadying his mind, which had become overwhelmed with love, Uddhava felt extremely grateful to Lord Kṛṣṇa, the greatest hero of the Yadu dynasty. My dear King Parīkṣit, Uddhava bowed down to touch the Lord’s lotus feet with his head and then spoke with folded hands.
According to Śrīla Jīva Gosvāmī, the fear of separation from Lord Kṛṣṇa was continually entering the mind of Śrī Uddhava, and thus he tried to maintain his enthusiasm by remembering the Lord’s great kindness upon him. He steadied his mind with feelings of gratitude toward the Lord.