It used to be 'don't worry, be happy' but it's now changed to 'don't put off until tomorrow what you can do today'. I quite like 'I won't die even if they kill me' though and plan to adopt that at some point in the near future.
I read Susan Jeffers book, 'Feel the Fear And Do It Anyway'. I've forgotten most of the book, but I try and live by the title. It's helped quite a bit with my shyness.
Just because you're paranoid, doesn't mean they're not out to get you!
Seriously, the only thing my maths teacher ever managed to make sink in was 'have the courage of your convictions' which I try to do. I sometimes regret this, as I hear myself saying things I perhaps shouldn't!
I quite like 'Carpe Diem' which I believe means 'Seize the Day'. Is especially relevant nowadays with all the natural and man-made disasters going on that you should try and enjoy each day as if it was your last.