I’m no expert on the Jesus Prayer, but I’d say at least say don’t judge it based on what you feel.
Hopefully someone more familiar with the practice can correct me if I’m wrong, but praying the Jesus Prayer is completely different than the Rosary. It’s not meant to be a set number of prayers and meditations, but an aid to praying constantly. After years of praying under spiritual direction, there are some who pray the Jesus Prayer with the rythm of their heartbeat.