The danger in answering this question at face value is that it can make you appear to look backwards instead of looking forward to what you can affect. There are a number of ways to answer it.
The first is to refuse to look back, and only talk about the future events you can affect. Make sure to at least mention the past as far as learning from it.
“I’m not a person who looks back at what might have been. What happened in the past happened. I learned from it and moved forward. I am organized and patient so that I can tackle what comes efficiently and with the best of my abilities.”
“I wouldn’t change a thing, because those experiences added up to make me what I am today. One thing I learned was that a good team, working well together, can handle any problem. That’s why, as a manager, I surround myself with the best possible people. As one of my former bosses told me, ‘surround yourself with people who are smarter than you.’”
Another way is to give a specific example, then explain what you learned from it. Talk about how that created a better outcome, or will create a better outcome in the future. Looking back is fine, as long as you don’t leave it at “boy, I wish I had done that differently,” without explaining how you’d do it differently.
“I was fired from my first job because I wasn’t meeting the sales quotas. I was working hard, don’t get me wrong, but now I know if hard work doesn’t result in sales, work harder. I’ve never missed quotas since then, in fact I’ve always exceeded them.”
“A few years ago a co-worker and I didn’t get along. We never talked about it, or communicated in any way, except to trade barbs. It hasn’t happened since then, but if I ever have trouble like that again I’ll sit down with the other person. If that doesn’t work, I’ll ask the boss to be a mediator. Communication is key.”
“I was notoriously late for my second job. They never fired me, I left when the company restructured, but looking back I can see it created conflict with my boss and some bad feelings with co-workers. After that, I’ve always been more careful to manage my time and to be on time all the time. My last boss commended me for always being on time.”
If the interview isn’t going well, maybe you’ll feel the same way as the woman who gave this answer. “I regret coming to this interview.”