Chanting should be performed with some feeling, whether the emotion is hankering for Krsna, remorse, repentance, eagerness to chant more attentively, remembrance of our favorite pastime or whatever. When there is some feeling our chanting becomes less mechanical and more spontaneous.
Interview for Dhanurdhara's Swami book, "Japa Meditations, Contemplations on Entering the Holy Name"