Why does the space on my iPhone randomly get used up?

I've had this iPhone 5S for a few months now, and I love it. It's a 16 GB (which is not enough, considering how much music I listen to).

About a week ago, I had 500 MB left on it, and I haven't downloaded anything since. I have surfed on Safari, and I have saved a few standard definition pictures from the Internet (no more than 15). However, now I have 0 KB of space left! How the hell does that much space get used up without me even downloading anything? I do get many E-mails, but I close out of my Mail app after each use (by swiping up while I'm in quick-select).

Is it the constant stream of E-mails causing this random decrease in available space? If so, is there a way I can reverse this and prevent it from continuing?

If it isn't the E-mails, what could it be, and what can I do about it?

It's everything. You don't have to download anything to use space. Closing an app has nothing to do with it either. Where do you think all of those texts messages, email replys, social status updates go? Thin air? No. They are on the phone. Apps are small in size but they can hold tons of data. See the example of my FB app. The app is only 107mb in size but is holding 1.2gb of data from photos, likes, replies, status updates, everything.
Your phone is just fat and bloated and needs to lose some weight. See under Settings > General > Usage to see which apps have you filled up.
Here's a couple of tips on how to manage storage space as well. Best luck. Http://www.imore.com/16gb-iphone-low-sto… Https://forums.radioshack.com/thread/113…

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