Seriously, never forget to breathe. It sounds like a stupid thing to say. But to actually try to think about your breathing could help you getting into an almost meditative state. It keeps other thoughts out.
The next step is to actually meditate. And that might be a bit to much for some people. So to think about your breathing is enough to help you in your everyday life. It can help you cope in stressful or uncomfortable situations. It helped me in tournaments and before big presentations at university.
The next step after that is to actually meditate at a Buddhist temple.
I did, for 7 days. It was great!