Man, I know I struggled with my first paver patio, walkway, and stairs that I completed at my brothers house but this stuff is just plain awful. It's not like a few bond lines are off, or some slight miscalculations on height, or something aesthetically unappealing. Half these things could have really bad consequences.
I will say this. One of the educational seminars I went to regarding building walls provides information and I wonder if people leave there thinking they are fine (certified) for building retaining walls greater than 6 feet, with major surcharges, or any other concern. I left that seminar confused/concerned more than ever that if I screw something up there are very bad consequences. The highest "wall" I've built is on a current landscape install and it's only one of those side of the house circles for a planting bed 3 blocks tall. It still takes time to level things and make sure it's correct.