Muay thai is inherently foreign to the Westerner. The techniques require you to purposely put your self off balance, and the ultra aggressive nature of the system goes against what society has taught us growing up. For example, think about your personal space and how uncomfortable it was for you the first time you did a clinching drill with a fellow student who you didn't really know.
The techniques, from round kicks to elbow strikes are made up of many moving parts all working in unison, and it takes a while to get comfortable with moving your body in that somewhat awkward way. For example, they say it takes 10,000 reps of the muay thai round kick before you get to the point where you can throw the kick without thinking about the technique.
It's very easy to get frustrated with yourself over the course of your training (it usually kicks in around the 3rd month in). But it's that over analyzing, trying to break down every component of a technique is what throws you off track. Ideally, you while training techniques, you're thinking about anything other than the technique that your practicing. If you find yourself getting frustrated with yourself, here's a couple pointers that I've found works:
1. Don't spend too much time focusing on a trouble spot. For example, you aren't pivoting on a round kick. Work on it but spending too much time on one issue will likely leave you neglecting the other parts of the technique.
2. Don't rush it! Throwing a crappy kick really fast will in no way clean up your technique. It's easier to throw poor technique quickly than clean technique slowly. Take your time, you aren't in a race.
3. Hitting bags and pads is fun, it feels good - but shadowing the technique is where you really make strides in cleaning up your form. Never neglect your shadow training.
4. This is the hardest part. Once you've practiced enough to where your body can physically throw a technique correctly (you understand the mechanics), then stop thinking about the technique while you're training. The ultimate goal is for you to be able to execute any muay thai strikes, whether it be kicks, knees, elbows, body movement - without thinking. It just becomes a natural part of how your body moves. Thinking, and over-thinking your technique will actually impede this. So think about anything else other than the technique - girls, work, school, does Taco Bell really use fake beef?
5. Step one in transitioning from muscle memory to subconscious reaction is to train thai pad drills where your partner calls out combinations at a pace that tires you out. And after you've reached the point of exhaustion, you keep going - s/he increases the intensity/complexity of the combos. Its meant to push you beyond the point where your brain cannot process the incoming orders, and its your reptilian brain & your body simply moving on instinct and muscle memory. That's where the real learning takes place.