My story?I always had a knack for algebra, but when I first encountered Calculus, I couldn't stand it and ended up "passing by memorizing". Very unsatisfying. But I ended up on a "winter camping trip" in the mountains one year, and there was nothing to do except read, and all I had was a Calculus book and some old newspapers. I would spend a whole day just reading and mulling over a single chapter, and something "clicked", and I finally got the idea of limits, differentiation, and integration, then spatial integrals of solids, and ultimately integrals in multidimensional space. After that, it was fun, and clear. I think people just have to be given time to let the concepts "sink in". They are rushed in schools nowadays.

Now I think learning what numbering systems are, and set theory, are probably more important for most programmers, unless you are in engineering-programming...then calculus is a must.