We're so careful crossing the street: we look both ways, we wait. But sitting down with our beads, we relax and let the mind wander wherever it likes. Yet Gurudev compares inattention in japa to vajra — Indra's thunderbolt, the one that grinds a mountain to dust. The root of all ten offenses to the Name is exactly this, carelessness. While you sit distracted, thunderbolts fall one after another and wound the heart, even though you don't notice them.