When legal personnel write letters on behalf of their clients, they often include a sentence saying "Our client reserves all rights."
There are good reasons for doing so. However, if a legally untrained person writes "I reserve all rights" (on his own behalf), it sounds like formal legalese, and may end up aggravating the other side's emotions.
Is there a way of rephrasing the sentence that preserves the meaning while not letting the situation get too emotionally charged?