Building self-confidence is not an external attempt to cover-up something ugly inside. Rather, it is the restoration of what is broken inside and anchoring it on something solid.
Insecurity is basically caused by experiences of neglect, rejection, betrayal, abuse, and abandonment, which all of us, in one way or the other have experienced. We carry these insecurities with us but cover them up with some superficial confidence. Eventually, these insecurities show up in different forms: control, vanity, indifference, lust, depression, and a host of other sicknesses and disorders. What looked like confidence at the start manifested itself as some narcissistic personality or bipolar disorder in the end.