Emotional control and risk management are the most important things that you must learn if you want to be a successful trader...when it comes to emotions we are referring to psychology, the most crucial part of trading...This deals with how well you handle losses and how you deal with the thought of not hitting your target..and lastly, knowledge too is important just as you mentioned, without acquiring knowledge you are just a gambler not a trader
It is very important to follow basic rules such as for example stop losses. Yes it will not save you from losses completely but it will significantly reduce your losses in trading. Beginners often make the mistake of starting to trade thinking they can manage everything manually without setting stops but when an unfavorable market situation happens they do not have time to exit the trade quickly and they decide to wait hoping the price will recover. This does not happen and they end up with very very large losses. I think this is one of the main mistakes.