He has tweaked his strategy a lot over the years.
He must still have confidence in it. People cant really trade a system after they lose confidence in it.
If you make enough mistakes its easy to lose money even if your system/method was profitable for a given year.
Strong discipline is required when trading, most of the time, except years like 2008 when it was easy to print money.
But most of the time you have to do almost everything right and the market doesn't forgive mistakes like missed signals so easily.
