A good rule of thumb in storytelling is that coincidences that help your protagonists will feel like the writer just cheated to get out of a corner they wrote themselves into, whereas coincidences that hurt your protagonist are more easily accepted.
If you feel you really need this lucky coincidence to save your character, you can fix that by going back earlier in the story and earning it. Your hero getting shot, and the bullet being stopped by a lighter in his pocket we've never seen before, will feel like a cheat. But if he helped a homeless guy earlier, and the homeless guy insists he take his lucky Zippo, and then the lighter saves his life, most people won't complain.
Just a little justification goes a long way, and helps make your world and story feel real and complex.
If you feel you really need this lucky coincidence to save your character, you can fix that by going back earlier in the story and earning it. Your hero getting shot, and the bullet being stopped by a lighter in his pocket we've never seen before, will feel like a cheat. But if he helped a homeless guy earlier, and the homeless guy insists he take his lucky Zippo, and then the lighter saves his life, most people won't complain.
Just a little justification goes a long way, and helps make your world and story feel real and complex.