Doubt is essential in challenging situations because blind optimism can lead to failure. Optimism is crucial for success, but there is a fine line between optimism and blind folly. Soldiers often fail when they overstep this line and become victims of their blind faith. The key is to balance optimism with a realistic assessment of the challenges ahead. Approaching any task with a spirit of doubt can lead to a more cautious and thoughtful approach, ultimately increasing the chances of success.