The gopis of Vrndavana were so attached to Krsna that they were not satisfied simply with the rasa dance at night. They wanted to associate with Him and enjoy His company during the daytime also. When Krsna went to the forest with His cowherd boyfriends and cows, the gopis did not physically take part, but their hearts went with Him. And because their hearts went, they were able to enjoy His company through strong feelings of separation. To acquire this strong feeling of separation is the teaching of Lord Caitanya and His direct disciples, the Six Gosvamis. When we are not in physical contact with Krsna, we can associate with Him like the gopis, through feelings of separation. Krsna's transcendental form, qualities, pastimes and entourage are all identical with Him. There are nine different kinds of devotional service. Devotional service to Krsna in feelings of separation elevates the devotee to the highest perfectional level, to the level of the gopis.

From Srila Prabhupada's Krsna Book ch. 35: The Gopis' Feelings of Separation