I struggle with my confidence, it's hard for me to maintain eye contact with others.
I completely understand. A lot of people struggle with having confidence in one's self.
Yeah self-confidence may be hard to build up. I think it depends on how a person was raised.
Yes it is difficult to build up and I'm sure history is a factor. It has a common meaning about handling events such as work, family, social events and relationships.
Yes, it can make one struggle in every aspect of life and causing emotional stress.
I agree! Confidence can be a self fulfilling thing as those who lack confidence may fail or not try because they do not believe they may succeed. And it can also work in reverse.
Exactly and it can block a person from doing their best because they don't even believe they can.
reference in regard to sport. Motivation theories have suggested that successful performance hinges on both skill and will. Yet, even a motivated and skilled individual can fail to perform if he or she does not have a personal certainty belief that s/he can handle what it takes or what needs to be done. Stajkovic (2006) argues that all three – skill, will, and confidence – are needed for action to unfold. The opposite of confidence is doubt. 
Core confidence.
Alexander Stajkovic argues that
her fame and how people think they know "everything about [me]" ("There's people talking / They talk about me / They know my name / They think they know everything / But they don't know anything about me"). As the chorus draws near, the song takes on a "party anthem" approach, where Duff discusses the "struggle" for joy and self-confidence: "I know I make mistakes / I'm living life day to day / It's never really easy