The best NBA coaches delicately walk the fine lines of their profession, hardwood Wallendas who avoid tipping too far in any direction. They must be authoritative without being militaristic. They must be approachable and communicative without being soft. They must be confident, without showing too much ego. They must employ effective strategy without micromanaging.
They also have to be chameleons, able to adapt to their talent, their circumstances and their era, and if they manage to do all this and be blessed with sufficient talent, they get to re-sign instead of resign.
Nate McMillan has shown enough of the necessary qualities in the necessary degree as an NBA head coach to boast a career that has lasted 14 seasons.