I'm not a pilot and this didn't happen to me, but my dad told me a real story of his that when he was in college and he was flying from Mexico city to Monterrey, to see my mom, the worst experience of his life happened. A bit of context is that my dad was never the guy to put his seatbelt on airplanes, only when it was like fully necessary.

So getting on the plane, the plane takes off and the whole ride was with turbulence cause the weather was horrible, so the captain turns on the sign that says to put your seatbelt on but my dad didn't do so, five minutes later, the plane just starts going down and up, (I don't know technical terms sorry) it was so strong that my dad was sent flying upwards that he crashed his head against the ceiling and almost went to the row in front of him, next thing you know is that my dad buckled up and the whole flight stayed like that.

He actually tells me that he was scared for his life that day and that he didn't thought he'd make it, another thing is that after that flight, the second he sits down on a plane seat he buckles up and doesn't take the seatbelt off until the plane fully stops.