Only twice?
I found a redundant steel bench where I worked. It was clearly a bit too long for where I wanted it to go, but I wanted it to fit as snuggly as possible. The shed was clearly an Imperial construction, although I had extended it slightly.
I was quite bilingual in both systems, so measured the space 'in English' - then I took the pencil note to work the next day, borrowed a tape and marked the bench with the section to be cut out - it was six-legged and I intended to remove the right amount from one side of the central legs, leaving it lop-sided, but the right size, after it was welded back together.
I looked at the cut-lines and it just didn't 'look right', so I repeated the exercise, over several days. But, whatever I did, it all came out the same and I had become more convinced that something was wrong. I didn't want to go through the whole cutting and rewelding thing only to find, as seemed obvious, that it wouldn't fit in the shed.
After multiple circuits of this procedure, I eventually realised that I was using two different forms of 'English measurements' - inches on one tape and feet + inches on the other, borrowed' tape - thus, I was reading my note of 96 inches as 9'6" and getting an extra 18".