We all learn a little at a time. When we do a particularly hard one, then when we go back to an easier one it is even easier than we thought because we learned so much on the hard one. Every two to three years I do an insane quilt like partial seams on a 1" diamond.
I keep to the basics. I try to cut accurately. I have felt pads every two inches on my ruler so it won't slip. I sew accurately by having 8 layers thick of painter's tape on my machine guiding my seam. It is one threads width shy of 1/4" away from my needle. I use the ruler I use to cut my fabric to measure that seam.
Go back to reasonable pattern for your next quilt.
Come back to this site with any questions. There are lots of smart ladies on this board