Over confidence is often irrational hope that the positive result would be achieved without correct evaluation of own strength and other parameters. One must first see the object, assess the strength and weakness and work out method. If properly planned, confidence will work. Confidence without adequate planning is over confidence that proves often disastrous.
Of course .... And people always underestimates other in this over confidence .. It is related.
There lies the problem. This is all right, you should be doing things your own way but not feeling that you are the only one who is right. all others are know nothing.
Even Amruth taken in excess turns to poison. Confidence is good. Actually, we need some confidence and trust in ourselves, to do our own things. But overconfidence may ruin everything. Pride is its another form
Over confidence is not a bad thing but it should be in control and we should be alert in our deeds. IF with over confidence we become care which is very dangerous thats why people say overconfidence is bad.
I will say one example my friend is first in clasee he had lot of over confidence he will become again first in class but unfortunately he became second because of over confidence he lost concentration on studies.