good question BS... but I am not sure I know the answer...
If I read the usual books on trading and believed what was said, then yes. Discipline, calmness and 'waiting like a sniper for the perfect trade to enter your crosshairs' are all attributes necessary to release the zen like money making maching within you.
However, seeing as the most succesful trader I know is borderline psychotic and rants and raves when he misses a move, I would have to wonder. The guy has made 10's of millions and the return on any one trade cannot have any impact on his wealth but he is very passionate and gets really, really narked when he (and his team) miss something they 'should' have got.
What I do think is that if you have a feedback loop so that you continually learn from good trades and bad, then you will move forward in leaps and bounds. Obviously - the psychotic guy does that by ranting and raving which shows lack of discipline but perhaps it's his way of ensuring things sink in.
In any case, I do believe that psychology is more icing than cake. I could be wrong though.