Most EAs will work only in a certain environment or condition the creator visualised. IF the end user do not have the same views, then chances are that it will fail. Whatever the EA can do, same thing each one of us can do manually.
I have a daily pip target to achieve. Whether others agree or not, I stand by this strategy, because I benefited from it; those who copied my trades also benefited. I will listen to everybody, but I will accept that which benefits me.
I do not believe in carrying overnight open positions and looking for a 500 or 1000 pip move to happen in my favour. I will break down this into daily targets and simply achieve it. That way it allows me to reach my target and allows me to test new strategies. But my target remain rooted to the time tested number of pips to be earned every day. While trying to get this target, I had losing trades too. That is a part of trading. I accept losses gracefully. I accept that I make mistakes and will make it in future too. But I am careful to see that losses are on the lower side and profits on the higher side. It is possible to remain profitable, but we throw away it in hope of a far bigger one which takes time to develop. Market are volatile and it never travels one way. One violent move against the trend for a short period and if it hits the stop loss, that is enough to turn the profitable trade to a certain loss.
This is what happens to EAs most of the time. Markets are unpredictable and will remain so forever. Earning 100 pips a day is possible, if one break it down into a couple of trades to achieve. If one is a full time trader, it is the way to go. If you dont have the time to be full time trade, then look for some other time tested strategy that will give you that result. I trust manual trading more than depending on EAs.