I took calculus and did well, but never could grasp the concepts which has annoyed me for years.
Personally, when I don't grasp the concept, I can't retain what I'm learning. The most basic is why taking the first derivative gives you position, the second gives you velocity, etc... besides reading this in a textbook or online, I don't understand why. In fact, I had to look online just to type that sentence because it never clicked with me.
Word problems was where I couldn't do any calculus. One word problem I remember was a swimmer swimming to shore at a certain speed while the water current was pushing him sideways at another speed. Where on shore would the swimmer end up after X time (I believe this is the correct question that was asked). While I understand the problem in hand, I don't understand how to apply calculus to solve it.
In my case, with electronics, such as inductor (v = L (di/dt)) I get the linear aspect of this. If the current went from 0 to 1A in 1s, and the inductor is 10mH (milli Henries), then the voltage is 10mV [(1A/1s) * 10mH]. But what does this really tell me if it's a 60Hz sine wave (AC voltage source)?
Anyway, sometime ago I came across a video from this guy, but didn't get too far into as I found following him was easy until I closed the video and tried to think about it further: