I respectfully disagree with those who suggest that the personality trait of risk-taking is part of the explanation of why David Petraeus had an affair.
There are different kinds of risk-taking. The General was courageous, which implies that he is inclined to risk bodily harm. He is likely insensitive to anxiety and pain.
There are financial risk takers, some of whom are courageous and others of whom are cowards in terms of risking bodily harm. I am a financial risk taker, sometimes brave in submitting to medical procedures, but more avoidant than most of physical danger. Literally, I bet what I consider for me significant sums of money most every day but I am afraid of taking a roller coaster ride at an amusement park and riding in a car with a fast driver.
Typically, generals are strongly motivated by achievement, will, or what I call power. Just because generals are courageous in terms of exposing themselves to bodily harms doesn't mean they take career risks. Careers and physical safety are unrelated values. We all know people who planned their careers carefully and proceeded cautiously, but on a weekend they are capable of jumping out of planes for recreational thrills.
Why might a general have an affair? To state the obvious, for sex. I suggest that, on average, the sex drive of men who cheat is much, much, much higher than the sex drive of those who don't.
There is a moderate correlation between the need for power and the need for sex. In other words, sex drive is significantly higher for leaders. (Based on the results of an analysis of 30,000 assessment of motivation from people on three continents: North America, Europe, and Asia,)
Why would a General risk career for sex? Perhaps he saw the risk of being caught or punished to be small. Maybe he has a long history of not getting caught. Maybe he knows a number of other powerful people who weren't caught and thought that is how it would be for him. ( This is perhaps the first time ever that the FBI investigated the CIA director. Who knew it possible? ) Maybe he thought he could keep it secret or manage the fallout if caught.
Men vary enormously in their commitment to keep marriage vows and in how much time they want to spend with their family. Obviously, breaking vows is about honor. Deep down many men who have affairs don't believe they are doing anything wrong. How do I know? Under conditions of anonymity they say so.
Men with a weak need for family are away from their wives for long periods of time.
Risk-taking is one of number of personality traits now being challenged by new information about what really motivates people. Like risk taking, attention seeking is not a unitary trait, because people vary in what they want others to notice about themselves. Some seek attention for their skills, others for their money, and still others for good looks. Humility is a third multi-determined, non-unitary trait we may need to re-think.
I don't expect to learn what really happened. The CIA is a secret agency. The General hasn't taken our motivational profile, which potentially would tell us exactly what motivated the affair. It just doesn't ring true to me that if the General saw significant risk to his career he would have gone ahead anyway. The General is an American hero, and while he may have erred, I wouldn't want to make sweeping attributions about his personality based on his having had an affair. His reputation may survive this, but it depends on what else is learned.