Reminds me of my screw up about a year and a half ago. I had only owned my Ultra 7 or 8 months and was still getting used to it's heft compared to my old Suzuki GT750. Riding from Upstate NY down to Friendsville, MD. Rain most of the way on back roads. I approached a descending, decreasing radius left turn a little too fast and hit the rear brake. You can probably guess what happened next!
The rear tire immediately started sliding so I released the pedal only to find I was headed for the gravel off the right edge. I was only going 25 or so and I plowed into the gravel and the bike went on it's left side.
I was lucky, no real damage (some scratches on the bottom of the left lower fairing). A couple young guys in a pickup stopped and helped me right the bike and I was on my way. But on unfamiliar roads in the rain? Watch out!