Not necessarily one that you abide by.
As I was skimming through the rather silly ‘No nos for adult men’ thread I suddenly remembered my division motto/mantra in the rok army which was 수사불패 청성투혼. The second half is rather lame and roughly translates to “I fight for the blue star (our division symbol)”, but the first half, 수사불패 (雖死不敗), is pretty badass. My best translation would be “though I may die, I will not (cannot) be defeated”. Read “su sa bul pae” in Korean.
Mottos in Latin, Chinese or Greek doubly welcome, as long as you provide translation.