This is not my story of course but the story that immediately popped in my memory when I read the title.
Steve Wozniak's story about rewriting floppy drive low-level software the morning of a big demo:
>I got it to where it was writing data on a track, reading the data on a track. Then I got it to where it was reading the data in the right byte positions. Then I got it to work with shifting tracks, and we wanted a simple program where we would say "run checkbook" or "run color math" and it would run the programs that were stored on the floppy disk. So we went off to Las Vegas, and Randy and I worked all night and we got it done to where it was working. At the very end, it was 6:00 a.m. and I said, 'We have to back up this floppy disk." We had one good disk that we prepared with the data hand-massaged to get it just right. So I stuck it in the floppy and wrote a little program, and I typed in some data and I said "read track 0," stuck in the other floppy and said "write track 0, read track 1, write track 1." There were 36 tracks—I had to switch floppies back and forth.
When I got done, I'm looking at these 2 floppies that look just the same. And I decided that I might have written onto the good one from the bad, and I did. So I had lost it all. I went back to my hotel room. I slept for a while. I got up about 10:00 a.m. or so. I sat down and, out of my head and my listings, recreated everything, got it working again, and we showed it at the show. It was a huge hit. Everybody was saying, "Oh my God, Apple has a floppy!" It just looked beautiful, plugged into a slot on our computer. We were able to say "run color math," and it just runs instantly. It was a change in time.
But the real eureka moment for me was the very first time I ever read data back. I wrote it on the floppy, which was easy, but read it back, got it right. I just died.
I think that Steve's entire interview is probably one of the most inspiring in Founders at Work:
http://www.foundersatwork.com/steve-wozniak.html