Walking down a dark alley, alone, at night and not having a sense of situational awareness. I was nearly mugged because of that, and now have a much greater sense of situational awareness.
I know, I know, blaming the victim is bad, but sometimes clearly assessing what led you to be in a certain type of situation can help you avoid those types of situations in the future.
There is an epilogue to the story: after the incident I crawled to the phone and called 911. The police arrived a few minutes later, and a few minutes after that told me that they had caught the perpetrator. The put me in the back of a police car and drove me out to where they had a hispanic kid, maybe 15 years old, sitting on the curb in handcuffs. They asked me if I could identify him and I said no, it was dark, I couldn't see anything but a muzzle flash. So they let him go. I have no idea if I let an armed robber back out on to the street, but I've never lost a minute of sleep over that decision.
You own your actions, not your feelings.
A lot about owning a situation is allowing yourself to do what feels right, not creating a plan for every contingency and situation. Muggings happen and they're very unfortunate and bad. But owning it well isn't as much about future prevention as it is trying to make sure that you still can have control over yourself afterwards. Sometimes things happen; why did some guy key my beat up old 95 Accord and not the dozens of other cars? Probably alcohol, but the point is less about the specific reason and more what you do in response and how you are able to gain control and feel comfortable.