Pretty much what Onur said. Not any setup fits your style, combined with how aggressive you are taking corners, brake zones and etc etc.
You could do great with a setup, but spin off on the first turn with another setup. Plus depends on what you use: Keyboard, Mouse, Wheel or Gamepad.
It's not the same to drive with an oversteer-ish setup than an understeer-ish setup. Same goes for braking, suspension, camber, amount of fuel (more fuel=more weight=less power-weight, also known as a slower car). Basically everything.
Have you tried to do some test laps using some setups from www.lfs.net/files