10/90 Principle

My dad sent me an interesting email about 10/90 principle a few days ago. The author, Stephen Covey, wrote a book Discover the 10/90 principle which I think is a really good one because this principle will change your life or at least, the way you react to a situation (although i've never read the book because i only saw the powerpoint slides. So what is this principle about?

10% of life is made up of what happens to you.
90% of life is decided by how you react.

What does this mean?

We really have NO control over 10% that happens to us,
BUT you can control the other 90% by your reaction.
You CAN control how you react.

And I find that this is really true.