A confident person never thinks himself as superior and always believes in the fact that others are superior in their own ways whereas a overconfident one thinks otherwise. The confident one always believes in continuous practice and learning while the one who is overconfident never believes in them. The confident one also realises that no body is perfect and everyone tends to make mistakes and they tend to rectify them whereas the other one thinks that they can never make mistakes. Finally the most important thing that tends to distinguish a confident one from a over confident one is the patience to listen to others which the first type of person does and the second doesn't.
It's not wrong to be confident but taking it a level higher could potentially turn the tables and there is a risk that you can loose everything in your life as confidence makes a looser into a winner but overconfidence makes a winner into a looser. So choose the path you want to tread on very wisely as one can make you and the other can break you....