I am not perfect - still learning like you - but I tend to cut things a little bigger in strategic places to give me a little "wiggle room" as Jenny at Missouri Quilt Co. calls it. For adjustment I use see through rulers. Yes, I have found that needle position on my Pfaff is unbelievably sensitive. Just one itsy-bitsy machine measurement is so effective. The main thing I remember of advice is to use the same machine from start to finish so the same adjustments adhere throughout the project. Relax and as someone else said, if you are getting consecutively smaller squares just make a smaller quilt "this project" and if need be, compensate in your sashing widths.
Marysewfun