Traders must have the perseverance to stick to trading until they break through to success. Many of the best traders are just the ones that had the strength to go through the pain, learn, and keep at it until they learned to be a success.
Great traders cut losing trades short. The ability to accept that you are wrong when a price goes to a place that you were not expecting is the skill to push the ego aside and admit you are wrong.
Letting a winning trade run as far as it can go in your time frame is crucial to having big enough winners to pay for all your small losing trades.
Avoiding the risk of ruin by risking only a small portion of your capital on each trade is a skill to not get arrogant and trade too big, if you risk it all enough times you will lose it all eventually.
Being reactive to actual price action instead of predictive of what price action will be is a winning principle I have seen in many rich traders. Letting price action give you signals is trading reality, trading your beliefs about what price should be is wishful thinking.
Great traders are bullish in bull markets and bearish in bear markets, until the end when then trend bends.
Great traders care more about making money more than any other thing. Proving they are right, showing off, or predicting the future is not as important as hearing the register ring.