This happens when the person is not calm/tranquil enough to handle the realization of no self (emptiness). One should also develop tranquility / calmness by doi

This happens when the person is not calm/tranquil enough to handle the realization of no self (emptiness). One should also develop tranquility / calmness by doing samatha meditation (like anapana). With having developed tranquility the realization of no-self and emptiness are easier to handle.