Viligence
Noun. Being BOTH vigilant (being alert, cautious, watchful of possible danger or difficulties) AND diligent (effort done with, or being steady, persistent, persevering ).

Adverb = Viligently
Adjective = Viligent
As a marine, even decades after his retirement, his viligence showed in his mannerisms, as he sat in the corner booth, his peripheral vision checking every person around him, his posture straight, despite his injuries.