Maybe just plain, old-fashioned good luck.

[Lt. D'Agosta tells Dr. Green about his good luck bullet that helped him become superstitious] Margo Green:
What have you got there? Lt. Vincent D'Agosta:
Good luck bullet. Margo Green:
Superstitious, I remember now. Lt. Vincent D'Agosta:
Yeah. Margo Green:
So does your bullet have a story? Lt. Vincent D'Agosta:
I was on the beat my rookie year, and I saw this guy who'd locked his keys in his car with his motor running. He's got a clothes hanger, and he's trying to get the lock off. So I go over to try to help him out, and what I didn't know was that he'd just robbed the liquor store a block away. So, he's concentrating so hard that he doesn't see me until I'm right up on top of him, and I surprise him. He turns, and... [D'Agosta makes a gun with his hand and makes a pop sound] Lt. Vincent D'Agosta:
Point-blank range. Doesn't pop, though. Doesn't go off. This bullet. [D'Agosta calmly holds the bullet out in the air between both of them] Margo Green:
So, what did you do? Lt. Vincent D'Agosta:
Took the gun away from him and beat the shit out of him. Anyway, the forensics told me later that the bullet's perfect. It should have fired. I should be dead. Margo Green:
So in other woods, a miracle of physics? Lt. Vincent D'Agosta:
Maybe just plain, old-fashioned good luck. [Margo smiles]