Acharya Prashant explains that fear arises from the mind's desire for certainty and its tendency to conceptualize future outcomes. He notes that even when one feels one hundred percent sure about a result, there is no guarantee that events will unfold as expected. Relying on mental assurance is futile because the universe is inherently unpredictable. If one depends on certainty to eliminate fear, the inevitable failure of expectations leads to shock and increased anxiety. Therefore, mental assurance has no real value in relation to actual events.