As a follow-up, is there any discussion and consensus about the psychological condition of the participants of these wars? Were they, as a society, less susceptible to trauma? Was 'shell shocked' a common condition?

I don't know about how likely they were to run from battle, but our understanding of PTSD and shell shock didn't really come about till WWI, so it wouldn't have been a concern. If one did run from battle or express fear, they were more likely to be mocked for cowardice than sympathized with.

There's some evidence to suggest that it was less likely to take hold in earlier wars that had much less protracted fighting. A battle before would have taken a day, maybe two. It was only in WWI that we started to see month-long offensives and conflict zones that never really stopped, and it was that extended period of stress without rest that really contributed to the rise of PTSD. And many of the early cases of shell shock in WWI were derided as being cowards. Before then, war was seen as a test of a man's bravery, and a good place to send children to help toughen them up.