Most of people are in quest of the grail, the EA that will indefinitly generates money when they will sleep and will go in holidays.
Regarding to the psychology aspect, we are unconsciously seeking the confort of the maternity when our mom was taking care of us, giving us milk, kinder, toys, etc ... we have at this moment some difficulty to enter in the adult age.
It's hard to hear, but it's the reality, this is the same thing with manual trading. When we begin, we think that the market will be inevitably advantageous to us and will go in the wanted direction.
In fact, we have to know that in front of us, there are other traders, tough guys with biger knowledge and larger capital, real sharks that will cut us into pieces before to eat us.
Expert advisors, as indicators are only tools that we can use to build our trading method.
When old traders say that markets change, it is not only a sentence, the markets really change. An EA can be exceptional during a certain period and catastrophic the next month / week / day / hour / minute / second.
We have to monitor EA to close bad trades or to simply desactivate it when the markets take another main direction.
Expert advisors have currently a fast evolution with artificial intelligence more and more developed than in the past, with neuronal networks, etc... but it will never forecast the market's movements at the perfection. As traders often said, the grail would be a time machine.