In the film, Kirk made some decisions during the "Harrison Incident" that will have a lasting impact on a lot of people, both on the Enterprise, Earth, and even on the Klingon homeworld. It certainly forced him to recognize that his actions have consequences on others, just as he had to face such feelings in the original series episode, "Where No Man Has Gone Before", where he had to kill his best friend, Gary Mitchell, to prevent him from destroying the Enterprise... it showed him the burden of command. I wonder ... will we see him he have to wrestle with second-guessing the decisions he made during the incident, and do you think that will that be explored in later stories (books, comics, next movie, etc.)?
by requesting the Enterprise be assigned to Marcus' secret mission, Kirk sent his crew on a mission that ultimately got them killed, and had serious repurcussions to many people living (and dying) on Earth. Do you think, following the incident, Kirk would need to deal with a lot of second guessing his decisions, and feelings of guilt? He did, after all, turn to his crew and say, very sincerely, "I'm sorry." For a man who bragged at the beginning of the film that he had "never lost a single crewmember", such a death toll in a single incident that he was in command during must have a significant psychological impact on the young captain? Might be an interesting area to see writers explore - how does Kirk come to terms with the decisions he made, the deaths that happened while he was in command, and push out from beneath those feelings, to learn and become the great captain he is destined to be...?