Hi there

This is the second time you have been worried about your performance at a veterinary practice.
From reading your description you did a very thorough job of disinfection and, in my opinion, this would be adequate given where I work has treated several confirmed brucella cases with barrier nursing etc. and I have personally had similar disinfection protocols after dissections - university setting (maybe not even as rigorous as you were!). If someone is not happy with your work then take that feedback politely, but take it with a pinch of salt as you did a more than adequate job.
There is a big problem with resilience in the veterinary profession and feeling that you need to be perfect all the time. I am a qualified vet and I've made plenty of mistakes. Training and working within the veterinary profession is full of both positive and negative feedback. Learning to take feedback constructively is really important and if I had a student reacting this way when I was teaching them or trying to constructively improve their professionalism, I would be concerned for their wellbeing in this profession going forwards.
Taking feedback and not letting it get to you is a skill, one I am still developing myself, but I really think you need to practice not letting these very small things get to you. How will you react when something really big does happen? How will you cope when an animal dies? When an owner complains? When a case deteriorates? Even when its out of your control.
My two rules with taking feedback that I have developed over years are as follows:
1.Who is giving you the feedback? Is it someone you respect and trust to have your best interests at heart? Is it someone who actually understands and knows what they are talking about? For example, a member of the public might not understand how a disease works so might be angry at you about an outcome when you have no control and they are actually upset at the outcome and not you personally. Grief can cause a lot of misplaced emotion.
If the answer is the feedback is coming from someone who knows and understands the situation, who you respect and want to emulate as a professional and who you know is trying to help you I move on to step 2. If the answer is the feedback is coming from someone who doesn't understand the situation, who you don't think acts like a professional you want to replicate and who is not being helpful or has your best interests at heart then I politely listen but won't take the feedback as seriously.
2.Reflection. So you have received some feedback about your performance from someone you know is trying to help you, who truly understands the situation and who you respect as a professional. Now, logically you think through if you think the feedback is justified....or not justified. Be kind to yourself, were you taught the protocol or not that you are being criticised on, you said yourself you didn't know where the materials were kept (no one showed you). If you weigh up why a situation happened, if you logically are responsible or if it was out of your control then often you find it might not be your fault.
With feedback it is important to be kind to yourself, sometimes it can feel like people constantly give negative criticism and that is exhausting. But change your mindset about negative feedback and take it as someone caring about you.
I know if I was talking to a colleague or veterinary student (I often teach the final years) about their performance, it would never be from a point of annoyance. It would be because I want to protect them from the consequences that I myself might have experienced. E.g. I had a student who made a comment that I know if a client had heard would cause a complaint. Making them aware of this so that they don't have that happen to them is a kindness its not to be mean and picky. It means I don't want them to go through a client complaint for a situation which I can predict with experience and warn them about.