Developing your own. I've been "developing" my S&P system for 10 years. I plan on simplifying it for robustness sake sometime this year.
My Forex system, which is a bout a year old now, is still under development but is coming along very nicely.
But it's true - no matter how good your system is or how right you have been in the past, there's always that bloody sticking second guessing. But I'm learning that it's not as important to be right all of the time as it is to be right when it counts. And that takes disicpline.