It's not really that simple. You can't really ever simulate your trading with 100% confidence since you're never entirely sure what your participation in the market will do to the results you see when you /aren't/ participating.
There is also plenty of anecdotal evidence that as you try and increase the amounts of capital you're putting to work in the market that it becomes tougher and tougher to maintain an edge in the markets.
There is also plenty of anecdotal evidence that as you try and increase the amounts of capital you're putting to work in the market that it becomes tougher and tougher to maintain an edge in the markets.