My suggestion is meditation and practice. If you were in Sydney I could give you a great place to learn the techniques. The rest is practice.
The mental chatter is quite normal. Its just thoughts jumping into your head. I've heard the untrained mind described as being like a small child running all over the place. Rather than your mind controlling you, you need techniques so that you control it. You can develop techniques to clear the mind and focus it.
The negative types of thoughts you're having perhaps look at cognitive behavior. The Buddhists have an interesting concept of suffering. As an example you're stuck in traffic late for a meeting and you get upset. Your late and that's bad however you add to your suffering by impatience and you make your suffering worse.
Or Yoda - Try not. Do or do not, there is no try. Very Zen Buddhist. Rather then focus on the future and what has yet to happen, live in the moment, the now, and focus on what your are doing. How does the bar feel, are you set, what does it feel like? Living in the present is important.