Ask HN: How do I improve?

I just recently started a new job, and I love it. However I believe I'm clumsy, there were times when I send out the wrong emails and several times I made mistakes on the emails. There were times when I didn't thoroughly test of my code, and end up having to do an emergency deployment to fix it. I feel like to talk too fast, and had to stop mid sentence to catch my breath. My supervisor said not worry, I'm still on my probation and that he expects me to make mistakes. I'm worried that I won't improve over time. Did any of you experience anything like this? How did you improve?