We are bombarded with messages such as these:
"Strive for excellence" - motto used at many institutions
"Strive to be happy" - Desiderata
"Striving and struggle precedes success, even in the dictionary" - S. B. Breathnach

A reserved person who is shy could be viewed as someone who wants to "stay in the background" and does not want to strive for something or achieve much. Reserved people are thought to be puahovers.

Why did Billie Frank start out as a background singer? Was it because she was shy/reserved?
Movie: 'Glitter' (http://www.wikipedia.org/wiki/Glitter_%28film%29)

http://youtu.be/hb4bsAuNmz8