Nature in this context would be things you have to get done except more of a belief that each person has a specific pre defined role. He's still very much talking about using discipline to accomplish this role and often self admonished for not getting more of his own role done.

Yeah, he's mentioning discipline being part of your "ethos" which Jocko would have plenty of experience living the SEAL ethos:

https://www.nsw.navy.mil/NSW/SEAL-Ethos/

If "the logos" (fate) declared Jocko to be a warrior, then it is well within his nature to be disciplined.