Having a healthy environment for your creative team means letting them experiment and explore. But there is no real experimentation without mistakes.
That's precisely why creating a culture where failure is accepted is so essential. Teams to be conservative in their way of doing and creating if they don't feel confident enough with their skills or the reaction from the management.
If you work in a group or lead a team, make sure you don't pressure your team to be perfect all the time. To avoid it and let them feel safer practice some of the tips below.
Laugh at them. Seriously, do it. Don't make a huge drama. If you do, people will fear to face that situation again, so they'll turn conservative and passive.
Run reflections with your team. Instead of focusing on the mistake itself, ask them questions so they can get to conclusions and avoid it happen in the future.
Don't let your team alone if they need you. It's true they should experience failure by themselves, but that doesn't mean abandoning them. Be close if they need you.