Sometimes beginners in trading do not realize the frustration they can get when they experience their first loss because most of them are already more obsessed with the profit even though they have not received it. Knowledge before doing something is very important, especially when it has to involve money directly like trading, so every beginner must have knowledge before they experience frustration that can cause loss of enthusiasm to continue what they have started.
That part hurt me the most when I started trading. Small losses do not even matter all that much and I can understand why that would not be really a big trouble but the reality is that if we are seeing something that is bigger then we are going to have something that will be a bigger problem. Think about it, you are just starting out and have just a few thousand dollars and you lose a thousand dollars, nearly half of your money, on a single trade. That was a terrible day for me, I did had like 30-50 even 100 dollar losses before and that did made me feel bad but not that too much and I was fine with it, but when I lost 40%+ of my capital all on a single trade, I really felt terrible.
Obviously it was a mistake to even have that much of my capital in a single trade but I was a newbie so I made a mistake. That had a learning impact on me, I learned that I should not invest that much into a single trade and ever since then I never did more than 5% on a single trade.