Jap-Man. An opportunity for us to disagree. That's a relief. I was hearing a rumour that we were related!
And disagree, I do. One of kyokushin's weaknesses is the lack of control its students have. This results in high attrition. It is never OK to hurt somebody by accident and then just move on. that is a wasted opportunity.
I'm not saying to mull over it and lose confidence. I am saying to think - how did this happen? Was it just bad luck? - if it was - then that's OK, and move on. There are accidents and there are accidents. If the accident was caused by a lack of judgement, a poorly executed technique, or even a loss of temper, those things are learning points. They will result in the maturing of the karateka, and ultimately create a yudansha who understands his or her own weaknesses.
I guess I am passionate about this because I have suffered qutie debilitating injuries in karate...at least one of them was a complete accident. No malicious intentt..just an accident. Buy my whole dojo learned from this. Nobody said "oh, it was just an accident...move on...wouldn't want to ruin your fighting by worrying about little things like unintentionally crippling somebody...". Don't misunderstand - I am not BLAMING..and I don't suggest we should. An innocent mistake is not a blameworthy act. But it is still a learning point, or the mistake will keep on happening.
Rxrliu's, I think your experience reflects exactly this. It seems to me that you don't understandd what went wrong here, so can't control whether or not it happens again. If you knew exactly how it had happened, you will either be able to choose to do that again in future (in which case, you won't be hurting by accident, it would be by choice - and that might be OK, depending on the circumstances), or you can choose not to do it. Then you wouldn't have to worry about facing that partner again. (and you will both relax, reducing teh chance of further injury).