How And When Confidence Become Over-confidence

Well we all know personally what is confidence and over-confidence. Confidence may be a firm believe in your capabilities, that i can do this/that. But on the other hand when you say this publically, People assume you 'r over-confident. Its just slightly difference b/w two stages. If we over-jump or exaggerate from the proclamation, It becume over-confidence. In literary context, it is like when you under-estimate others it is called over-confidence.
Sometimes, we say this is only a work i can do, but people assume you 'r over confidence. e.g Bret Lee say " I am great bowler, no-one can compete me in speed ". Half of the people say he is over-confidence, But i think he is claiming what he got, and he is best.
However, its kind of debate, i want you guys views about, what is confidence and over-confidence and What is that specific point where confidence becomes over-confidence?

Thought provoking topic. I agree with the above. There is a fine line between confidence, overconfidence and conceit.

Confidence is belief in one's abilities and implementation of those abilities in a practical sense. It is saying I will not give up in the face of obstacles and pitfalls. Not only a desire to do better but an ultimate goal and the determination to be able to meet that goal keeping in mind difficulties. Everyone should have such a quality that eludes a defeatist mentality. Where as, I believe overconfidence is overestimation of one's abilities. The idea that you not only can but will accomplish anything and everything that comes your way. Now there is no harm in having such a positive attitude, but sometimes that can lead to disappointments because one should be able to realize there will be hurdles and that words do not make achievements, actions do.

Lastly, an absence of humility defines conceit. Confidence is asserting one's capabilities as well as being thankful for them. Conceit is simply boasting without any real value to back up the claim.

If you say I can jump from the 200 Meter Height into swiming pool very easily, its confidence but if you say I am the only one who can do that than "That is over confidence"