One of the points made by this book, as well as an academic article by Steinke is on how figuring out ways to apply the material you are trying to learn is more useful to the learner than memorization (full source and citation at the bottom of this post). This is because you are thinking critically and using problem solving:
"As a pedagogy, service-learning inherently teaches the kind of thinking skills and knowledge application necessary for success outside academia."For this reason it is always important to think about how something is applicable when you are learning it, especially if you have a terrible professor. "How is this equation important or useful to something I might do?", "Why am I learning this?" And "Is this course work important for what I want to do after school?" are all important questions to ask yourself time to time. If you can't answer these question, it might be time to reevaluate your academic priorities.
Steinke, Pamela. "Assessing Service-Learning." Research & Practice in Assessment 1.2 (2007): 1-8. Penn State. Web. 23 May 2011.