Five Finger Death Punch - Brighter Side Of Grey Lyrics Meaning

It might be about him leaving his family to go to war but he's telling them he will be waiting on the brighter side of grey, meaning that the brighter side of grey is when he comes back home. "When the lights go down, Know that I am never far away" could mean that when the war comes, he could die, but he will "always be with the family" (In their hearts).