My advice is to never do less than 30 `good repetitions’ of anything when you are seriously practicing kihonwaza (fundamental techniques). Obviously this can also be applied to technique/sequences from the kata, such as the mawashi-geri from the ground from Unsu, chudan morote-uke in Heian-godan and nami-ashi from Tekki-shodan. Of course this even more so applies for kumite (sparring) and goshin-jutsu (self-defence) as the elements of distancing, timing, psychological control, and so forth, are added to the equation.
If a technique, kata or application is giving you trouble, just train until you get it right. Keep practicing and the answer will come, and if not, during your recovery times, seek advice and study. However, drop the `Western mindset' that study and mental understanding is training, because IT ISN'T. Everything understood by the mind most be done repetitively by the body. That is, to be effective, the motivation of the study/advice seeking must originate from physical training. Once mentally understood, it is put into physical practice (= REPETITIONS). This is the cycle of development in karate, but never forget, that repetition is the pedalling, and without pedalling, the wheels on the bycycle will not move. "Mou ikkai!" "OSU!!!"
© André Bertel. New Zealand, 2010.