Srimad Bhagavatam Canto 10, Chapter 35, Text 01

SB 10.35.1

sri-suka uvaca
gopyah krsne vanam yate
 tam anudruta-cetasah
krsna-lilah pragayantyo
 ninyur duhkhena vasaran
 
Translation: 
 
Sukadeva Gosvami said: Whenever Krsna went to the forest, the minds of the gopis would run after Him, and thus the young girls sadly spent their days singing of His pastimes.
 
Purport: 
 
Although the gopis enjoyed direct association with Krsna at night in the rasa dance, during the day He went about His normal duties, tending His cows in the forest. At that time the minds of the gopis would run after Him, but the young girls had to stay back in the village and do their own duties. Thus feeling the pain of separation, they would sing about Sri Krsna’s transcendental pastimes.
Srimad Bhagavatam Canto 10, Chapter 35, Text 02-03