Many years ago I asked Sensei if he had ever talked with his father or grandfather about their time in the military or in combat and the bad things they must have experienced. He said the only thing his grandfather said was, "War is war and things happen, shoganai." This is something that has always stuck with me. Shoganai or shikataganai are responses, but they are more of a state of mind that you utter in passing when you get some unpleasant news or when something bad happens. They roughly translates as that there is nothing you can do so just accept it and move on. The spirit of shoganai is what enables Japanese people to pick themselves up and move forward after something untoward happens. I wish it was something that I could take advantage more in my own life, but I think it has to be engrained in you so that it can be automatic so that when something unpropitious happens I can just utter shoganai and move on. Maybe not dwelling upon adversity is one of the biggest differences between the Japanese and the Americans. In Japanese traditional arts and especially in the martial arts adversity is seen as something that helps the student grow. The teacher tries to create an environment to push the student toward change and ultimately his greater self. It is thought that most students or young people have iji or stubbornness and resist what is good for them. Therefore a teacher is supposed to instill in the neophyte konjo or fighting spirit, but in order to do that the teacher must create an environment for change. This change can sometimes be unpleasant as is most change. So adversity isn't seen as something to dwell upon, but more of something to surmount. How do the Japanese do it? First they say, "shoganai" and then they move on and get over whatever adversity is that they are presented with.
I remember this scroll written about in Tea life, Tea Mind that read, "Be rebuked, stand corrected and learn." Within these sagely words we can see the root of shoganai and the fighting spirit of the Japanese people. Please train hard.