I'd completed college algebra and took a statistics class, and was enjoying the math so much that I decided to go for calculus. Loved it! Understood it completely.
I asked several of the math teachers why, after failing miserably the first time in high school, I was doing so well thirty years later. To a person they said, "Oh, Poindexter. People don't realize that it's a developmental thing. A lot of students just aren't ready for it when they're 17, but give it a year or two and they will be." Clearly that was the case with me.