关于一句话意思的困惑mens sana in corpore sano(sound mind in sound body

关于一句话意思的困惑
mens sana in corpore sano(sound mind in sound body) is my motto,and,not even to be funny,am I going to make believe that i don`t know what the Latin means.I feel that the least that Ican do is to treat my body right when it has to supply fuel for an insatiable mind like mine.
第一句话的后半句not even to be funny,am I going to make believe that i don`t know what the Latin means为什么要用双重否定,作者是想表达怎么样的思想感情啊?