Modding on the Spectrum

There are two interns at my company as of late. One day, I was alone with them in the office. The telephone rang. I told them that I usually don't answer the phone (due to social anxiety but I kept the reason to myself). So they asked me whether they should answer the phone instead. I was already in panic mode so to speak. I couldn't think clearly anymore and said yes. Big mistake that was punished a few days later. My boss called me on Friday. One of the interns answered the phone anew but this time an ad customer was on the other end of the line. She told the customer to call back on Monday, however the closing date for advertisements was Friday. The correct answer would have been that he should have tried again later the same day. My boss reprimanded me for telling the interns that they can answer the phone. They hadn't yet received any instructions at that time. We should have let the phone ring. I told the boss that I was in panic mode. He said it would have been better - after the panic mode was over - to address the matter in order to find a solution. I didn't even think of it after the first incident because I thought everything was fine. Now I've spent the weekend thinking over and over again about my misbehavior and dreaming up horror scenarios for the consequences. I even went so far as to visualize the dismissal on my desk. When I greeted the boss on Monday morning, he immediately noticed that I had something to say. I said I was sorry. He didn't know what I meant at first. He remembered when I told him I was sorry about the phone thing. He replied something along the lines of "just sponge it over" and that there was a weekend in between. So it wasn't as bad as I had imagined! He also liked that I thought about my mistake - a quality that sets me apart he said - very few people do that in his opinion.

How can I think about my (big) mistakes without imagining such horror scenarios again?
What mistakes did you do in your vicinity? Were they as bad as you had imagined? How did you deal with them?

TL;DR: I made a (big) mistake at work. My Boss reprimanded me last Friday. I've spent the weekend thinking over and over again about my misbehavior and dreaming up horror scenarios for the consequences. I even went so far as to visualize the dismissal on my desk. I apologized on Monday. My mistake wasn't as big as I imagined. How can I think about my (big) mistakes without imagining such horror scenarios again? What mistakes did you do in your vicinity? Were they as bad as you had imagined? How did you deal with them?

I'm not experienced in these situations, but as a regular with two interns I would try to overcome my anxiety, how ever hard that would be. It could be a possibility to overcome that anxiety in the long run. Try to prepare for such situations when you're not at work, but in the safe environment of your home. Stand in front of a mirror and imagine you're in such a situation, being the only person to be able to respond to such a call. Just pick up the phone, how difficult it may be, and respond with something like "Sorry, but there's nobody around right now and I'm not qualified to answer your question. can someone call you back later today?".

Just my thoughts, and no idea if it can help you, but the only things I could think of.