The road was too slick for your tires to maintain traction in first gear with the available engine braking power. You should have pushed in the clutch to get your steering and used the brakes with ABS to maintain control of the vehicle. Perhaps you are not as good of a snow driver as you give yourself credit for??? Now you can say that you have been in a skid that you "didn't" know how to get yourself out of. Glad you weren't hurt.