Some say in trading the true character of a person comes forward with all its strengths and weaknesses. Suppose a trader has a tendency to be perfect, to perform each and every little task in perfection. For people with perfectionism, it may not be that hard to function in everyday life, maybe with a little struggle here and there. But it's very hard to combine perfectionism with trading.
As we have seen so often, a significant part of trading is the acceptance of being wrong in many, if not most cases. A trader 'suffering' from perfectionism would have a hard time dealing with all the failing trades. A perfectionist trader will always find something that could have been better in every trade. Such a trader could start negative self-talk and blame himself for all the mistakes, missed opportunities, wrong trading size, etc. Doing such negative self-talk will most likely influence his ability to recognize new trading setups in the market, resulting in even worse performance and more negative self-talk.
It's not easy to lose perfectionism, but there may be a way to tone down negative self-talk. Pretend not to be talking to yourself, but to a colleague who just completed the not-so-perfect trade. Try to bring criticism, but in a rational and positive way. Discuss the failure as something you and 'your colleague' can learn from. That's what colleagues are for ;-)