Studying Mathematics is totally different from studying Humanities, this is the reason why humanities students often don’t do well in maths. But with the right studying techniques (i.e. practising doing mathematics), humanities students can be very good at maths. Together with their creativity and good memory, humanities students have the potential to achieve the top grades in maths exams.
I have taught Pure Literature students and found that they definitely have the potential to do well in Maths once they learn the correct method of mathematical studying and thinking, and how to approach solving Maths questions.
One of the top mathematical physicists, Edward Witten, majored in history and minored in linguistics! (http://en.wikipedia.org/wiki/Edward_Witten)
Mathematics is not a spectator sport
Even if you understand every word in lecture and in the textbook, the only way to really learn mathematics is by doing mathematics. Sometimes this means doing even more than the assigned problems. (See “time committment” above.) This is how to avoid the common pitfall of “understanding everything in class but blanking out on the exams.”
I realize this isn’t welcome advice, and I admit that I haven’t always followed it myself. But in years of teaching (and 20+ years of learning) mathematics I haven’t found any shortcut.