CC Antya 18.16-17

bhakta-premāra yata daśā, ye gati prakāra
yata duḥkha, yata sukha, yateka vikāra
kṛṣṇa tāhā samyak nā pāre jānite
bhakta-bhāva aṅgīkare tāhā āsvādite
Synonyms: 
bhakta-premāra — of the ecstatic emotion of the devotee; yata — all; daśā — conditions; ye — which; gati prakāra — mode of progress; yata — all; duḥkha — unhappiness; yata — all; sukha — happiness; yateka — all; vikāra — transformation; kṛṣṇa — Lord Kṛṣṇa; tāhā — that; samyak — fully; pāre jānite — cannot understand; bhakta-bhāva — the mood of a devotee; aṅgīkare — He accepts; tāhā — that; āsvādite — to taste.
Translation: 
Kṛṣṇa Himself cannot fully understand the conditions, the mode of progress, the happiness and unhappiness, and the moods of ecstatic love of His devotees. He therefore accepts the role of a devotee to taste these emotions fully.