How to get over a fear of theft?

Last October my cell phone got stolen in school. One day later I got it back. I'm afraid it is going to happen again once I get the iPhone. I'm very afraid it is going to get stolen in the school locker room. How can I prevent it from being stolen again and how can I get over this fear?

Valuable things grow legs when you leave them laying around. My cellphone is either in my pocket or in my hand, no place else.

You don't.
If you leave it out of your sight, it will probably fly away. Just take better care of your things, if you simply must leave it in your locker, put a key-operated lock on your locker on top of the combination lock if possible and keep the key on your neck. If possible keep your phone on your hip at all times.

People are greedy, and often lack respect for others.