I have done it so many times that now I don’t even write the numbers down any more. I simply mark on the tape measure, when it has to many pencil marks on it, I simply throw it away and get a new tape. If I have to use a measurement out of the workshop, ie, go buy stock, I make a note on my phone along with the current project buying list. My phone is never to far away, including pics of things that may need a better description once I get to the hardware store. if I’m not sure of the proper name of an item, the pic saves me a lot of time describing something to a box store kid what I’m after. I have even taken a pic of the tape measure to eliminate my second guessing.

Don’t feel bad Brian, I suspect most of us have done the same right/left mistakes many times. I think it’s partly because we get enthused with the idea that we are making a duplicate and forget that it is a mirror image.

My woodworking mentor rarely made these kinds of mistakes. He was able to focus very clearly on this kind of spatial object thinking. Me, sometimes I measure twice on a completely different number. 60-13/16 becomes 61-13/16. I get so focused on getting the 16ths accurate that I completely overlook the fact I’m an inch off. That actually happens so often that I remeasure 3 times to make sure I’m in the right location and I still mess up sometimes. The worst is when I’m rushing things, of course.

I usually mess up when there are right and left pieces . I get done cutting and I have 2 rights or 2 lefts . Man I get so mad at myself .

If it makes you feel better:
I cut the drawers for the buffet I am building. and recut tem 2 " shorter the following weekend out of the blue. Lost 3 drawer and some expensive veneer:)
I am still kicking myself you know were. My wife had a great laugh.