Cass,

Don't let it get you down. I think it was around my own 6 month mark in Aikido, that I too started having the frequent feeling of "why can't I get this right!?!" I think it's probably part of the learning process that most of us go through. (I'm coming up on 5 years of Aikido, just for reference)

For me, it largely went away after my 4th Kyu exam; that's certainly not to say that I never screw up my techniques (I do, often), but the way I've accepted correction has changed. It's gone from "Why can't I get this right!?!" to "Alright, self! Let's do this next repetition correctly" [or at least "do it better", depending on how far off I am] followed with a verbal "Hai, sensei!"

Building this sort of true humility (i.e. focusing on correcting yourself, without being angry with yourself), also helps you survive the pressure when a Shihan calls out your technique during a seminar as being an example of "Was not anyone watching me? Do like this!". OK, self: give a brief embarrassed expression, breathe... "Hai, sensei!" ...copy what sensei just did. Hey, success!