Using the same strategy will not the trader always making profit, but if the losses continue, I think you should re-analyze and try new strategies according to current market conditions, or maybe this is time for you to take a break from trading activities or lift your knowledge about other strategies then use it, could be the new one is more suitable for current market.
Maybe, a trader must have to move on and find out what makes him wrong. It is probably not because of the strategies a trader is using, it probably he might be too emotional. If this is found to be the reason, I don't think you will be able to succeed but certainly just about to fail no matter many tries you do as will always ended up losing their minds and make bad decisions.
"Never trade with emotions" is supposed to do in trading. But somehow, many were still got the influence of this, and not to wonder why they keep complaining their losses.
Strategies do play a role as well, there are bad ones that could make you lose money and a bad trader could be using a horrible strategy to keep on losing money as well. However I agree that 90% of the bad trades that end up with a loss probably comes from being emotional and making moves that is based on wrong emotional hectic moves.
I don't know the real number, it could be a lot less than that but I feel like emotions are the number one reason why people lose money in trading. Even the simple fact that "buy, if it drops then buy some more, then when you are out of money keep on waiting, wait until it goes to profit, sell" is out there and people still lose money. I am not saying it will guarantee you profit, but waiting and not getting any panic on the drops should be number one way to make a profit, whereas many people still fail to do that.