Haven't read all the responses but this was me. High school physics was the first time complex math made sense to me. It was because I wasn't doing math just to do it - it was math with a purpose. I always want to know the "why" behind what I'm doing, and my math teachers were of the "just because you have to learn it" mentality. Math made sense when it was part of a bigger picture, not the picture itself.
I admit that I don't always understand how my 5th grader has been taught to do something, and I find it frustrating, but when we figure it out I usually find that he's learning the number sense approach, which I never learned in school. My husband gets it right off the bat, though, and I suspect it's because he was like a lot of you and figured out the number sense part on his own. Whatever we call it, I'm happy with any method that helps my kids internalize and understand the work.