Sewa means getting into the divine service of lord, and this is our only goal. But that would happen after Bhagwat prapti. What before that? Guru is the representative of Lord on earth, so do sewa unto him, do whatever pleases him, follow his sayings, do Roop Dhyan, shed tears for bhagwan, and if capable then do Daan. Making him happy, makes Shyama Shyam Happy automatically.... Radhey Radhey.