I remember when I did once return from shop rather quickly, it was of course winter time and there was bit of ice and such.
Anyway, there was few concrete blocks and I needed to squeeze between them, then needed to make hard right that wen't big of uphill move sucseeded well, I drifted about 5 meters cycling with quite quick tempo while my shopping were in plastic bag that did hang from brake lever, however I did not take account of shopping bag inertia, of course it swang back and my drift did not stopped. End result was that I drove about 25kph to brick wall that was next to street, bent front wheel and wall got few nasty marks, after I found out which side was up, I just crab remains of my bicycle and started walking towards home, only bit over 1km left so I was lucky I guess.
No helmet of course, was not used back then, I don't think that they even did sell those in shops widely then.