It generally means that a strategy is optimized for achieving the best results on a particular data set to such a degree that makes it unworkable on new data.

This is a very common problem and there is no concrete solution for it.

I suggest you do not use the Optimizer for now. You can validate your strategies with  Monte Carlo and perform future validation on a Demo account to test your strategy reliability.

After I optimized my EA it showes the good results , but when I ran it on the chart the result was not good, i give the new data sources to the FSB and the result was the same with the real work of the Ea , so I optimized it after I give it the new data sources , it shows a good results again ... but again in real work of ea the result is not satisfying,  so what is the use of optimizing the EA?? Just to correct itself in backrest? ?? What about the real work of EA. ? I feel like wasting time. Please help if you can help..