Dr. Mann while making a point that he is doing the right thing, says '...This is not about my life, or Cooper's life, it's about all mankind. There is a moment...' and then gets blown away by the explosion.
All of us atleast a few times must have felt we are facing a defining moment. A moment that will choose a specific path for us. We feel like we would look back at this moment with a historical importance not attached to regular times. We feel this is the moment we have to push harder and rise above the constraints of human possibilities.
For some, there is a desparate search for these moments to define ourselves.
The reason to search for defining moments is based on our common reading of history. We define history in terms of a sequence of defining moments. Battle of Stalingrad defined the course of world war 2. French revolution defined the course of modern human organisation. Newton's theory of gravity defined the course of scientific revolution.
While it's true that we cannot ignore the importance of specific events in history, we should see them as a the culmination of processes and ideas long before them. Battle of Stalingrad is the culmination of Hitler's decade old fight to alter status quo and the world's resistance to it. Newton said he is standing on the shoulders of giants while proposing his theory of gravity. French revolution is the culmination of the inherent conflict of the old ideas of political organisation with the spread of literature and freedom of expression to the masses.
With our own life too, it is the daily routine over a long time that defines the path ahead. There are no defining moments. Every moment defines us. We are what we think and do all the time. We are not how we act in some moments. That way, waiting for defining moments is an exercise of futility expressing our own inability to correct our daily routine.
