"It's difficult to hear the things you can improve on because you want to hear 'you're so good, you're so good.' It's really difficult, but it's one of the most important things ever, especially on a 14-person roster where we're so close ... We can affect how each and every one of the people on our team plays just by saying a few things, so that was huge." ~ Natalie Hagglund, U.S.A. Volleyball libero
The way you see yourself is not the same way other people see you. It's impossible to be completely self-aware on your own.
Other people see your behavior. You can only see your intention behind the behavior. Other people hear what you said. You can only remember what you meant to say (h/t Steve Pike). It's the reason Karch Kiraly recently implemented a peer review system for USA Volleyball in which players anonymously evaluate each others' behavior.
It's easy to understand why something like this is rarely used. It's uncomfortable to be told where you're faltering and equally uncomfortable to tell someone else where she's faltering. But given that so few teams are capable of doing it well, the potential rewards are enormous.
The key is that Kiraly, "would have considered scrapping the idea altogether had his players said no way ... 'If they were not open to it, I would have have been far more loath to go ahead with it,' Kiraly said."
Indeed, something like this could completely backfire if players aren't open to it. But if players aren't open to honest feedback, that creates an entirely different set of issues.