I'm not exaggerating when I say that it was quite by accident that I found this way of wording, "Mistakes are welcome." For a long time, I thought that if I actively encouraged students to be okay with making mistakes in front of me that I was an ineffective teacher. I find that there is this pervasive thought in most of my students that if someone fears making a mistake that they are less likely to make it.
I actually find the opposite to be true. The more you fear a mistake… the more it's a self-fulfilling prophecy. You keep imagining you will make the mistake. You keep thinking about making mistakes. So what does your brain do? It does what it keeps thinking about. It makes mistakes.
Ironically, I have found that when you make mistakes something that is not to be feared, the brain then just sees it as an option, not a forbidden thing. When it's an option, your brain then has the ability to choose what it wants to do. Choice is a powerful thing. It's kind of what makes the brain a very cool thing. We can choose what we want to do, we can forge our own path in life. Mistakes are a part of making choices, and it's great to make mistakes if we also learn from them.
So stop beating yourself up. Mistakes are welcome. :)