It doesn't happen a whole lot, but are these moments roughly just general, completely harmless "bumps?"

For example, tonight a heavy duty storage container lid fell from about five feet above and conked me on the head as I was on the floor assembling a desk. It's a large 27 gallon container from Costco by the Greenmade brand that reportedly weighs around 14-15 lbs empty; unsure how much the lid weighs, perhaps around 5lbs, and it's a very tough and sturdy material. The part that hit me was the toughest side portion.

Obviously it's not Mark's example of a bowling ball falling from a couple feet. I'm probably a bit overwhelmed since I've been helping someone move all day and something dropping on my head's certaintly not what I was hoping to happen before a long drive.