this Strategy has passed some Test like, monte carlo, Walk Forward and Optimizing and i get strategy have Good Line (Circle Blue), but when Try it to New data (green box) , the graph is drawing good line at the frist time (Circle yellow), but at the end time is falling down(Red Circle)..  and i get Similiar result again, again and again…

How to avoid this Case ?..

i though mybe some Special Action can avoid this Case like

1. what Acceptance Criteria do u use ?…
2. what timeFrame do u use ?..
3. how much data bars do u use, or Range Of Date?..
4. what preset indicator do u use at frist time?..
5. what setting generated like “Strategy Properties” or “Generator Settings” do u use?..

any suggest ?…

Thank you