I found this quote via tumblr and fell in love with it immediately. It reminded me that there's a rainbow after the rain and no matter how life sucks - in every sense of the world, it is still beautiful.
Optimism is never a sin, it is a blessing. Opting to see the goodness in the world decreases worry and stress. Therefore lessening the chances of diseases - making you live your life longer.
This doesn't mean that you have to live a totally worry-free life (I think this is more unhealthy). Just learn to move on, let go and live life the way you wanted it.