To unenroll from a course, go to your Lagunita dashboard page at lagunita.stanford.edu/dashboard and click on the settings gear icon to the right of the course image. A drop-down menu will appear. You will want to select the Unenroll option.
Note that there is no penalty for not doing all the work in a course. You are welcome to complete only the activities that interest you – there is no obligation to pursue a Statement of Accomplishment if you are solely interested in learning the material or just curious about a topic. If you find that a course has more work than you can keep up with, consider just watching the lectures or finding a similar compromise.