There is no such thing as "confidence" as a general term. Confidence is context-specific. Let me explain:

Let’s say that you’re a highly-skilled heart surgeon. After years of schooling and training, and experience in the operating room, you’re as confident as it gets on the job. You’re tops in your field and you know it. Now, just as you leave the operating room, you go into the waiting room and see that a terrorist has left a nuclear suitcase bomb in the waiting room! There’s 2 minutes until it blows, meaning there’s no time to call the bomb squad. You open the bomb and see a bunch of wires and parts, and your confidence drops to ZERO as you realize that you’re clueless and powerless in this situation.

Suddenly a man in the waiting room sees what you’re doing and comes to help you. He calmly reaches into the device, turns a dial and pulls a wire, and the timer on the device stops. He doesn’t even look scared! In fact, he looks extremely confident. You ask him how he knew how to stop the bomb and he proudly says "I designed this weapon. I worked for 25 years at Los Alamos building nukes. Turning it off is child’s play." Now your heart is still racing at this point and the stress hasn’t gone away yet, and all of a sudden you have a heart attack and stop breathing. The nuclear bomb technician has no medical training whatsoever, not even a first aid course. Suddenly HIS confidence drops to ZERO as he realizes that he’s clueless and powerless in this situation, and he calls for help.

The above story illustrates my point: There’s no such thing as a "confident" person, only a person confident in areas he’s very familiar with. If you have no skills and experience dealing with something, you won’t have any confidence in dealing with it either!