"There is a great difference between worry and concern. A worried person sees a problem, and a concerned person solves a problem."
- Harold Stephens

Song 'Don't Worry, Be Happy' by Bobby McFerrin:

https://m.youtube.com/watch?v=d-diB65scQU#

Was Rocky worried before his big match?

Movie: Rocky
http://youtu.be/sHrlDDznJLc

"Worry is a form of fear, and all forms of fear produce fatigue. A man who has learned not to feel fear will find the fatigue of daily life enormously diminished."
- Bertrand Arthur William Russell

Fears lead to effects such as worry and depression, but it does not have to be that way. Fears can be overcome.

Song 'Don't Worry Be Happy' by Bobby McFerrin:

A "happy go lucky" person lives by the motto: Don't worry, Be happy.

http://idioms.thefreedictionary.com/happy-go-lucky