On a demo, even though it's live data, your fills are from the application and not the exchange so when you go live it feels a little different... another thing is there are no consequences to trading on a demo so when you go live and real money is on the line emotions come into play big time and change the course of your entries and exits and decisions you make or hesitate to make. Everything adds up...Why is that? What was different?
How can it be a profitable strategy if it fails when you go live?