To the original poster: Hang in there my friend. If you live thru that series of mistooks, take a deep breath and look out for the next one to come along.
Even tho i nivr mak mistooks, i could rite a bok on some of the things that have happened to me. Not mistooks, just that they happened.
for now, maybe the easiest to straighten out appened when i was still in the masonry biz. I was to put in a garege foundation and pour floor on a hillside. I was able to lay out for footings with only one step down. About 3/4ths of the building was on level ground with the last 6' had a drop off of about 8' down. I had to setup with transit from two locations, but having had lots of experience with working on hillsides (Hey, this is Connecticut. I have been on so many hillsides, one leg grew shorter than the other), I assured the owner i would have no problem getting the foundation level and square. I had once put in a house foundation with a 20 foot dropoff. the footings had over 30 steps altogether. This would be a piece of cake. The owner, being a builder, was somewhat skeptical. He had the attitude that anybody wearing a beard was some sort of a kook. In those days, we were thought of as hippies.
I set my batterboards and lined the ground where the footings were to be and went to work with my backhoe. I had ordered concrete for mid afternoon and was home enjoying a cold one when the phone rang.
"Tinker, I think you have made a mistake."
"Phil, impossible. What do you think is wrong?"
"I think the footing is too short"
"I don't see how that could be. I checked everything before i started digging." I went on, "I'll come over and check it out right away." Lucky for me i didn't argue.
Later that evening, I called back. "Phil, being a carpenter, have you ever measured a board to be cut at 6'6"? You used your 6' rule, made a mark at the end of the rule and then a second mark at 6" and then cut the board at the 6' mark?"
"Yeah, i guess I probably have done that atleast once."
"Well, i measured 20 feet and then added 8 feet to set my corner stakes. Unfortunately, i used the 20 foot lines to dig my footing along the back." It took me longer to straighten out the problem than it had taken to do the original excavation, and due to minimum load allowances, the concrete was actually more expensive for the relatively small correction than it had been for the entire job--- had it been done correctly in the first place.
AND, that was probably one of my very least expensive mistooks (remember, I have nivr mad a mistook. Those things just come along and sneak up on me when i am out to lunch :

)
I could probably fill up quite a few pages of a book with mistooks. [dead horse]
Tinker