I have been doing my own work for 53 years, so I have made lots of dumb mistakes. Here are just 2:
I don’t use my 99 Volvo wagon much anymore, so I often put the charger on the battery to keep it alive. One night, I needed the wagon, so I went into the garage, opened the middle door and, walking in the dim light, closed the hood of the Volvo, got in, and backed out. Hmmm. What’s that slight scraping noise? Moving forward, no more scraping noise, but a thump as I run over something. I get out of the car an find the flattest battery charger on planet Earth. The scraping noise was dragging the still connected charger out of the garage.
Back in 2007, I was doing the first oil change on my wife’s new Infiniti M35. I had just moved the pan of old oil to someplace where I wouldn’t trip over it, when my then 16 year old daughter came out the remind me that I was supposed to drive her someplace. “Yeah, yeah. Just give me 5 minutes…” I get in the car, start it up and look underneath to check for leaks…no leaks. Shut off the engine and start to walk into the garage and just stop dead when I see the unopened case of new oil in front of the car. With the distraction, I had forgotten to put oil back into the motor. I had visions of a $10,000 bill to replace an engine with 3,500 miles on it, but there must have been enough oil on the bearings from running the engine just before the oil change, because 100,000 miles later the engine is still running fine. Dodged that bullet.