the TLDR is I am looking for a book to relearn Calculus. I finished Calc 3 past semester, but despite high nineties in all my Calculus classes, I don't feel like I learned much motivation for what I am doing and with my Calc 1 and Calc 2 far in my mind (took a leap year), I often find myself having to google how to do improper integrals or to wonder the reason why something works. I can do problems all day with relative ease, but the why of it all is mostly a mystery.
I did some research and Spivak, Apostol and Courant were the textbooks that seemed to fit the bill. Still, I am not settled yet on which one I should go with or if I should go with them at all. I also don't plan (currently) to read all of them, so if I go with Spivak, I would not bother reading Apostol volume 1.
Looking forward to your recommendations, and thanks in advance.