Is self-confidence the key to success?

In order to succeed in life you must have self-confidence.  Self-confidence is the amount of ones belief in ones ability.  That's great, but how does this work?  Do I need to believe in myself more or do I need to acquire more skill or both.    

Let's consider believing in myself.  How far can that take me?  Can it compensate for a lack of skill?  The answer is yes.  We have all witnessed people in sports, business, etc., achieve beyond their capabilities.  We call them over achievers.  However, are they able to sustain a high level of performance?  The answer is most cannot.  They have had their 15 minutes of fame.

Let's consider ones ability.  How far can this take me?  Can it compensate for a lack of belief in ones self?  The answer is yes.  We have all witnessed people in sports, business, etc., who trained and worked hard to achieve success.  We call this the American Way.  Can people continue to succeed on hard work alone? 

There is one common denominator that is implied in the formula for self-confidence.  It is success.  You have heard it said, "Success breeds success."  However, success is not possible without self-confidence.  That brings us back to the original question, how does this work.

The definition suggests the amount of ones belief is the key.  If so, how do I assure that I have the right amount of belief.  If I have less ability, do I need more belief and vice versa.  I think we all struggle, some more than others, believing in our abilities.  That is probably a good thing because if we did not, self-confidence would be replaced with arrogance.