I was riding my ninja 250 today. It had rained earlier in the morning but when i left the house it was just drizzling. Everything was fine on the highway but once i got off and was riding on regular streets, i encountered some problems. On two occasions i tried to engine brake by downshifting at low speeds and both times my rear tire skidded. The first time was no big deal but the second time i strayed to the left and had to save my motorcycle from falling. Is this normal? This is the first time i ride in the rain. What did i do wrong?