The next time you are typing on your iPhone, whether it be a text, a blog, a post, an email - If you want to start over for any reason - JUST SHAKE YOUR PHONE. It is the fastest and easiest way to undo what you just did. Once you shake it, it will give you the following option:
Click on undo and everything you just typed will be gone and your off to a fresh start!
GIVE IT A TRY!!!