I have found a couple things help me pretty reliably. Listen to something calming and repetitive like white noise or rain sounds. Then have a mundane thing to think about and focus on. I will visualize starting with a cube of wood and slowly cutting the edges and corners of to make a sphere. Or imagine I am cleaning a flow with methodic sweeping and mopping.
Other people have suggested good info to gain nuisanced knowledge. I recommend starting with a simple fact. With enough time and/or the right conditions all storage will fail. Design your setup with redundancy. I personally had to replace 2x 12tb drives this year. I have raidz3 (3 parity drives) and a hot spare. So I just bought cheap replacements from a reputable seller on eBay and consider it part of the cost of self hosting.
My guess is the motherboard manufacturers could get away with this in the past without any issues. But Intel is pushing chips so close to redline out of the box that now it causes problems.
A used older desktop is a good starting machine. I think Unraid is a good starting point as the community is more welcome to completely new people needing a lot of help. Also this channel has a tone of good guides for Unraid:
https://youtube.com/@SpaceinvaderOne?si=A8BWLbMq42KzHD8I
I suggest starting off cheap to learn. Then you can spend money as you determine what is necessary based on problems you encounter. One VERY important thing to remember is that HDDs fail, power surges kill motherboards, water leaks kill the whole thing. If you don't want to loose family photos, MAKE SURE YOU HAVE IT BACKED UP OFF YOUR SERVER. Preferably "off-site".
Try to slow down and think about it from your bosses view. Assuming they are a reasonable person, they don't WANT you to be sorry. What they WANT is you to not make those mistakes. So instead of saying sorry, consider doing a "retrospective". Consider what went well and what could have gone better. What lead to mistakes? Can we take steps to avoid or mitigate those mistakes in the future? I don't know what kind of job you have and it may be impossible to do that on work time. But if you come to them with and understanding of what lead to mistakes and a plan to improve, they will be more interested in that than you says sorry 50 times.
Please note, I understand this is a challenging ask. But making significant improvements in life usually are. Also results are not instant or permanent. It's a process you keep working at, but get better at over time.
Reading that makes me feel like you are supper wound up. I know a challenge I am working on is being so focused on what I am doing, that I don't pay attention to what I am doing. I am working on forcing myself to stop and be mindful. Also running helps. Hard to get supper wound up if your exhausted.
I remember this being covered in a college engineering class. It's an issue of synchronous vs asynchronous communication. In person, phone call, instant messaging are all synchronous with an expectation of a timely response. Email and text are asynchronous with an expectation of inconsistent and/or delayed response.
I know how I feel about a situation is often dictated by my expectations. Hopefully this is a useful mental model.
In general checkout LearnLinuxTV on YouTube. Lots of good guides.