What happens if your phone dies?
What happens if your phone dies? If it went all the way to 0%, the phone would simply stop running, you would loose all unsaved progress, and important memory may be corrupted. Just like when the power goes out and your PC dies. To avoid this, iPhones (and other phones) automatically shut down when the battery is almost empty.
Is it bad if your phone dies fast?
If your phone's battery is draining faster than usual, it either means you're using a lot of energy or your phone is not using energy efficiently. This could mean you're overworking your phone by running too many applications, or something is physically wrong with the phone battery itself.