In prema, pure divine love, there is meeting and separation. During meeting there is external meeting, and in that happiness, the devotee forgets everything internal. But during viraha, separation, he or she remembers the pastimes of meeting. Meeting with the Lord is certainly one type of happiness, but separation is another type of happiness. Therefore, sādhakas (practitioners of devotion to Śrī Kṛṣṇa) in this world perform bhajana in the mood of separation by remembering the pastimes of Śrī Śrī Guru and Gaurāṅga.
Srila Gurudeva - March 20, 2008 Navadvīpa