Army Medical Appeal Watch
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Just saying that you are medically fit now doesn't change that you have self-harmed in the past and it could be you've been rejected as it was more than one episode. What does it say in your rejection letter? That's what you need to be specifically writing an appeal about.
You'll see from other threads on here that the Armed Forces are very strict on mental health, so you can try an appeal, but understand that it may not be successful.