I took Calc I course and currently studying Calc II. I'm pretty good at integration and differentiation in terms of mathematically solving equations, but I don't truly understand the concepts.
When I apply integration rules to a solve a problem it just feels like magic to me, so I don't really get what's going on. For instance, if try to a solve an unfamiliar application problem I won't really be able to solve it. I feel like I'm just a useless calculator. At the beginning, When I started to learn about differentiation I had a pretty good understanding like finding the instantaneous rate of change, and understood the relation distance => velocity => acceleration (and why it works that way). Now I lost track.
I want to be able to use these concepts creatively in real-world applications. Can you suggest a book or a give me an advice on how to truly understand these concepts?