For people to feel comfortable sharing honest feedback with me, I have to resist the urge to interrogate them when their feedback isn't what I want to hear. Often, the reason it's hard to hear is because there's a grain of truth.
To make it clear that critical feedback is welcome, people need to be confident that I won't get defensive. It's not worth it for them to risk a confrontation when they have nothing to gain. It's easy for people to tell me what I want to hear, but that doesn't help me grow.
To keep everyone in a positive mindset, I ask how I can improve the next time I'm in a similar situation rather than asking what went wrong. Since the future hasn't happened yet, we can work together to describe how it should work next time.