First of all, your boyfriend or husband is not your “opponent.” Thinking of him that way during a discussion will compel you to treat him accordingly. If all you’re trying to accomplish is to get your point across and win the argument, you both lose.
The above paragraph comes from the book Make Him Beg For You Attention, I'm not quite sure the meaning and the grammatical facts of it.
What I thought about the meaning is that both of your aims, get your point across and win the argument, will be unsuccessful according to the contents. But if so, what is the grammatical structure of the sentence? Why not using you lose both?
If I see the sentence alone, I think 'you' is a determiner and 'both' as a pronoun which represents the couple is the subject and lose is the verb. So the meaning will be both of the couple lose