How can I bridge derivatives and integrals in Calculus for real problems?

[Grace.M]

I'm a college freshman struggling immensely in my introductory Calculus course, specifically with understanding the conceptual leap from derivatives to integrals and applying them to real-world problems beyond the textbook examples. I attend lectures and do the practice problems, but when faced with a new application question on an exam, my mind goes blank and I can't figure out how to set up the problem, which is incredibly frustrating because I need this credit for my engineering major. For students who successfully made it through this hurdle, what study methods or resources finally made the concepts click for you? Did you find particular online video series, study groups, or a different approach to practicing problems that built the necessary intuition, and how did you move beyond memorizing steps to truly understanding the underlying principles?