It's never pleasant, but having falls is just part of bicycling. A couple of years ago, I went down on an MUP I had ridden a lot. I hit a shady spot on a curved incline that was still damp, and though I was going slow, my back wheel slid out and I hit the pavement hard. My right hip had a really bad contusion and elsewhere the normal road rash. One always needs to have some caution and awareness, but no matter how diligent one is, things happen, sometimes in a split second. Just be grateful you were not seriously hurt, remember the lesson, make sure all is good to go with the bike, get back on it and ride. FYI, look out for wet leaves on pavement.