Check, double check then check again. And if you are not sure do it again.
"Stuff like this makes me wonder if I, still very much a child, have any business in this reloading stuff........"
I started reloading when I was 14, I was mostly unsupervised. The only mistakes I have made have been in the last few years, well into my 50s. Youth is not an impediment if you have the right mindset. Age is no advantage if you lack the right mindset. Fortunately for me my mistakes were minor, reading load data for a 350 grain bullet in a 416 Rigby then using it with a 400 grain bullet for example. I noticed the mistake after I shot the loads then was loading them again. Deliberately check everything, caliber, bullet weight, powder type, powder weight, etc, etc. Then check it again, then check it again.