When does one decide that an obstacle is impossible to pass?

I have several blocks: Knowing the difference between their and there, APA and MLA formating, Java and C++, Parallel parking and speaking French, trig and logarithms, and critical thinking. Should I bang my head against the wall and try again or should I explore new goals? The definition of insanity is trying over and over and expecting different results. So should I try again and again to learn to overcome my blocks or try something different?