Can I speak up for the teachers who always bear the brunt of the 'it's your fault I can't learn it' syndrome. Try and bear in mind that, perhaps even uniquely, maths is a subject that it is very easy to forget how hard it was to learn, if you had difficulty with it. The better mathematicians often make the worse teachers as to them it seems eminently obvious. The ones that do make good teachers are those who've understood what it is that enabled them to learn it. Simply put mathematical knowledge is primarily about learning to follow rules.
I often hear students say 'but I don't understand why' and they are using the word understand wrongly. For instance, if we want to understand temperature, we mean its cause and such - the kinetic energy (and rms of the velocities) of the particles and such. But in maths that isn't what you want to understand. You can perfectly well apply the Law pV=NRT without know in what p, V, N, R or T mean by just following the rules. Perhaps more mature students realize this more easily (not that they may do so explicitly). As another example, I firmly believe maths at high school level (in the UK, approximately the same as freshman and sophomore years in the US) would benefit from people thinking of it as learning French, or Spanish. You wouldn't try and read Sartre in the original wihout learning the meaning of at least a few words; and that is perhaps a better approach for maths too. The student who writes x^ax^b=x^{ab} has not failed to understand what exponents are, but forgotten the rules of their use, just as a student who writes je regarderez has forgotten the rules of French grammar. But in maths the reason for the rules is also derivable to help you remember the rules - you can remember what cos differentiates to (everyone knows it's sin or -sin) by thinking a little about a picture - but they are just rules.
