What makes a great trader is execution skills, one can be the best analyst and have the best setups edge and plan  but lacks the execution skills, can still lose money.
Having said that what gives a trader good execution skills is having a clear ,confident, calm patient and disciplined mindset in order to be able to execute with confidence and without hesitation.
We see things as we are not as they are, so everything we do is a projection of our internal emotional states, beliefs, and mindset.
If we bring our default  scarcity mindset to our trading, focusing on outcome( PnL) ,and trading not to lose, and the need to be right,  we will be trading emotionally out of fear, hesitation, and lack of confidence, which is our default human mindset when it comes to handling risk.
On the other hand if we train and rewire  our default mind to focus on process rather than outcome , accept losses as part of the trading business cost, bring abundance, focused, patient mindset, while accepting risk…etc we start rewiring our emotional brain and response system,, and take fear and threat our of the game, and we start responding rather than reacting, and following our plan more consistently  and execute with more confidence and patience.
Of course this is easily said than done, since  what we bring to our trading is our conditioned emotional and behavioural patterns from younger years, so how we react to, losses, impatience, fear, ..etc on a subconscious level is reflected in our trading decisions and in our account pnl. This is where all the work lies when it comes to trading psychology and performance.
we need to change our behavioural patterns and overcome our discomfort, and rewire our emotional triggers, in order to trade consistently and profitably.Each individual is different, and find different ways to deal with their emotions patterns.
So for a trader to be consistently profitable, he has to bring a consistent mindset, in order to follow the plan consistently,  and be able to observe his emotional state and behavioural patterns that don’t serve him well, this is done but cultivating self awareness using mindfulness practice in order to become observers of our thoughts, feelings and emotions,  and learn to detach and let go from negative emotional patterns.Taking breathing breaks is very helpful during the trading hours to rejuvenate the mind and regulate our emotional state.
I can talk more about how the mind works and the different mindsets and how our brain, mind and  emotional states affects our decision making …etc, but you get the idea and I don’t want to bore you much:) 
Hope that helps and sheds some light on how crucial having the right state of mind  when it comes to trading and how it affects our decisions and results.
Everybody can make money in trading trading, the hard part is keeping it.