I am an undergrad that will be a sophomore in the fall, and I've completed the first level class in calc-based classical mechanics, as well as Calc I and Calc II. The math presented to me was a typical plug-n-chug, cookbook, focus on techniques rather than concepts style. In short, I don't understand anything about calculus despite getting A's in the classes. I'm a mechanical engineering major that wants a solid mathematical foundation to take with me into higher level classes and hopefully grad school. I'm starting with Apostol vol.1, and I've realized I haven't had a single exposure to a rigorous text of this type before. All of my required textbooks have been watered down nonsense that don't teach you much... So...what should I do to best understand the material? Take notes on everything I think might be significant? Focus on proofs only? Try to prove proofs by myself before I look at them? Study the proofs only until I can work out the problems? There seems to be a theorem-proof-example-problem type of style that I have had yet to encounter. How do you guys organize your self studies? Do you keep an organized binder with separate sections for problems and notes, or do you just use a spiral notebook and ignore keeping super organized about it?