I think the most important thing to become a trader is to control your emotions. Many new traders often let their emotions overwhelm and they often make the wrong decisions. If you have negative thoughts while trading, it is best to stop and resolve those emotions before returning to your trade.
But I think emotion is not even the primary thing. What I think every trader should do or know is to have and believe in their strategy. After that strategy, then emotion can make you a good trader because you understand when to trade (I mean making a call order) or not because of the strategy you already built.