There are two kinds of confidence: the inner confidence that comes from the very core of one's personality and the outer confidence (a lot like Dutch courage), which is more superficial as it comes from the approval of all the other people surrounding one and is used like a cloak.
There are pros and cons for both.
The inner confidence is harder to come by, if you are not born with it. It does require maintenance. But once you have it, it feels great, it is part of who you are and no one can take it away from you. You always feel comfortable about yourself no matter what. Those who know you often wonder how you do it.
The outer confidence is much easier to get for anyone. Just put on a display, or get a new haircut, or a new pair of shoes, or the same item of clothing to fit in. And you are done. But it will run out comparatively quickly, and also underneath those layers you still feel shaky and, well, like a fraud, quite frankly.
So, any little thing like a careless remark of your friend or a strange look from a passerby can knock it down.
This kind of confidence will help you to get your foot in, but to keep up the act is going to be quite a slog.
In an ideal situation you would have the both: the inner confidence presented with a dash of the outer confidence which will grow on you and they gel together. That's when you feel not only unbreakable but also able to shine and attract others. This kind of confidence is more likely to last and survive life disasters too.