Small studies are good exercise. When I teach workshops I often ask the students to tape off a canvas into quarters for a couple of reasons. It helps to keep the student from turning the study into a painting and the small scale forces the painter to just deal with the big shapes. Try taping a 12×16 off into 4 panels and give yourself one hour to comeplete each study. Set an alarm if necessary so you don’t end up picking it to death. Big shapes, color notes, color relationships and no detail.