I have been teaching subjects involving math for many years (more than 30), Operations Research, Probability and Statistics, Micro- and Macro Economics, Game Theory - to name a few. Almost always, most students struggle. After all, mathematics is just a language, and a fairly simple one as well. I have come to the conclusion that the real problem students have is not necessary learning the language, but learning how to apply it. That is, the abstraction of defining variables, parameters and relations between, not only to preserve inherent logic, but also to construct a model which produces results. what do you think - agree?