There's an newspaper advertisement for a diving watch saying that:
Accuracy is everything when your life hangs on one breath
- Any grammer mistake here?
- What do you think it means?
It means that when you are diving you have to rely on your equipment. The watch is part of your equipment and you are relying on it to be accurate as it is your reference for time and action. The advertisement is saying that you can trust your life to the accuracy of this watch.
The statement is fine in the context it is used.