Here is something that should work for you, it's really Tai Chi.. but hey.
1. Get into the stance you want to work on, settle into your center, clear your mind, feel the flow of energy, sink into your feet. Pretend you are hip deep in honey, so that you have to move your feet by lifting rather than falling. Make sure your breathing is deep and slow try inhale for 4 count, hold for 6 count, exhale 4 count, wait 6 count then breath again (slower when you get dizzy).
2. Slowly do the technique, a single strike or single combo. Notice if you come out of your center and then do step 1 again. Do at least 30 reps of each technique at very slow speed, the slower the better. Make sure you are totally relaxed and centered.
3. Once you can do the technique 10 times in a row while maintaining center then speed it up. If you feel any tension or lack of balance or thoughts that are not about what you are doing, then go back to step 1. I tend to do a new form 100 to 500 times at slow speeds before I try full speed.
On the mental side, don't think about the technique, keep your focus on your center and let the movement happen with no attachment to outcome. Once you can just let your body guide you it's amazing.