Most dangerous mistake at age 16. Outdoor pit at abandoned gas station. Going to put lowering spring shackles on my 1934 Ford convertible - my first car. It had one transverse spring front and rear. I took off the old shackle and BANG! The spring came down hard. If my hand had been under it.....Now, with darkness approaching, how was I going to lift up the end of the spring and slip the pin in the new longer shackle? I fought panic. Fortunately, my good friend Charley was with me and in his car was a scissors jack. He managed to wedge the jack under the spring and lifted it up while I slipped in the pin. Mission accomplished. I won't mention the several times I put new points back in the wrong order and the car would not start, We've all done that.
Latest mistake. Three days ago, I tried to replace the cabin filter in a 2002 Honda Accord I was trying to sell. Fighting my bad back, I took it apart with the aid of a video but wouldn't you know, after dismantling the plastic trim pieces and a few screws, I found that one of two remaining small Phillips screws was stripped and the other could not be budged. I didn't feel like dealing with the two remaining screws and didn't want to pay a mechanic to complete the job, so I started to put it back together. I replaced the small panel in front of the gearshift knob and now it was time for the big panel. But wait - where did the last screw for the big panel go? You guessed it - under the small panel, so I had to pry it off again. Next day, I took the new cabin filter back to NAPA and got my 28 bucks back. Let the new buyer deal with the stripped screw and the recalcitrant screw.