Why can’t I be over confident?

I don’t understand when my confidence turns out to be overconfidence..

Is there a gap between the two, segregating them?

Have you identified that gap..?

A positive vibe is there in ‘confidence’ while it becomes negative in overconfidence. Why do people tell in this way?

Self-confidence comes from within. So why should one be bothered on what others do?

Above all, does it really matter, whether it is confidence or overconfidence..? Even if it is over confident, either we will work hard to achieve it or we will fail and learn from the mistakes..so what’s wrong in being either way?