From The Great Gatsby a dialogue between Tom and Daisy:
"you're a rotten driver", [Tom] protested, "either you ought to be more careful or you oughtn't drive at all"
"I am careful"
"No You're Not"
"Well, OTHER PEOPLE ARE", she said lightly
"What's that got to do with it?"
"they'll keep out of my way" she insisted, "It takes two to make an accident"
"suppose you met someone just as careless as yourself"
"I hope I never will" she answered...
Those familiar with the book know that Daisy met that random person that triggered a tragic chain of events later in the book...substitute a few words and you summarize this debate in a nutshell
Please, Please, Please: Be prepared for the worse that society has to offer. It may be a random event, and a small probability...but violence is rampant in our world.
Forget worrying about a scratch on the bike, carry something that helps to keep you safer. All you're trying to do is make yourself a more difficult target.