I Am Breathing In

So, here's the thing.  I'm a super anxious person with a mind that won't quit...ever.  I worry about stuff, I psyche myself out of things by overthinking and by brain simply just won't shutup.  I've read about people who can live in the moment and I often think how glorious that would be to never lose sleep over anything.  I've tried saying to myself "I am breathing in, I am breathing out" but immediately, not even a half second later my mind starts to race.  I know for a fact, you can shut off your brain, walking around the streets of Edmonton has shown me that several people know how to do this, although, I think for alot of them, it isn't intentional either.  I need to know HOW!  How do I control this over active mind to allow myself not to worry about every darn thing and just allow myself to be content with what I am doing NOW?!