The main reason why most trader fail in trading is that they are not trained in the craft, most experience traders as they call their self don't even know how to identify the least support and resistance, talkless of knowing how to react when they see some certain chart pattern or candle stick pattern.
The skills I believe that are required to come out profitable in trading are;
* Knowledge: know the craft, know what you are doing, don't trade on assumption.
* Know how to control your emotions: it's very important that you know how to control your emotions like fear and greed in trading.
* Know how to manage your risk: knowledge and emotional control gives you money, but proper risk management skill protect your money and your gains
most mistakes of traders are;
* Thinking it's a get rich quick scheme or thinking that it's easy.
* Having no proper training in the craft to attain knowledge about it.
* Watching one two or three video's on YouTube by one YouTube influencer and think they are ready for it or thinking they have known the craft.
* Having no experience traders that is good in the craft to guide them.
It's always best to earn knowledge and use it for your trading as there are many factors that may affects your decision making and yes, like what you said, greed mostly conquer you and manipulate your decision, once you follow that greed it will start directing you and commanding and instead being contented with small earnings you'll choose to push for much larger and eventually you'll lose your position, part of that is the volatile nature of this business.
You can't just ignore the quick pump or the quick dump and your usual reactions is to move according to the trend hypes, and that's the worst thing in trading, emotions should not be tolerated but instead use the earn learning and follow your setup strategy from time to time.