Check your brakes!
I crashed my bike this morning.
I was riding down Commercial Street to meet friends for coffee like I do every day, and I noticed a truck ahead of me was slowing down. I applied my rear brake, nothing really happened, so I pulled the lever for the front brake and boom - right over the handlebars!
A car behind me stopped to make sure I was okay. I got up right away, noticed my knee was bleeding and checked the arm that took most of the brunt of the fall. Scrapes and a little blood but no significant damage. I pulled my bike out of the street, picked up my coffee cup, found my phone, and waved the car driver past.
I texted a friend to let him know I'd crashed and wouldn't make it to coffee, hopped back on my bike, and meandered home to clean off the blood and grit and put on some Band-Aids.
So why did I crash? My rear brake was worn out and I applied the front brake way too fast. Apparently using the front brake suddenly like this is such a common cause of crashes and injuries that it has a name: the "endo," short for "end over end."
So, lesson learned: Do an ABC check before riding, do more bike maintenance, and make sure those brake pads are up to snuff!
Analysis of the Bicycle Endo http://cozybeehive.blogspot.dk/2009/10/analysis-of-bicycle-endo.html?m=1
ABC Basic Bike Check at the League of American Bicyclists: https://bikeleague.org/content/basic-bike-check