I think this is a common mistake made by beginners.
Its best to work on crib/lap quilts and learn quilting tecniques
before jumping into a big project like a bed quilt. This then causes frustration and you become overwhelmed.
When frustrated you forget the basics,
cut accurately and sew your 1/4 inch accurately.
You have invested money for the class as well as fabrics so you should continue the class and take it one block at a time, and learn from the class and the other quilters.