Yes I believe a person can increase their self-confidence and over come insecurities. The first step of course is to learn to LOVE Yourself. One of the best ways to do this is by (stop) telling yourself negative things or having a negative internal dialouge. You have to continue to (feed your mind) with positive thoughts about yourself and well as visualize yourself having the kind of the life you want. Stop worrying about what other people think of you. They aren't inside of you and therefore will never really know what it's like to be you. "Life is a personal journey".
Adopt the philosophy of knowing the only person you can control is you. This helps you to keep things in perspective. What is the sense of worrying and stressing about things you have no control over? Having said that each of us gets to (choose) our own friends, lovers, and spouse. If you go to the grocery store to purchase an apple but buy an onion instead....Whose fault is that? Hopefully with time we gain enough wisdom and experience to know ourselves better and make better choices for ourselves. Our lives are pretty much the result of our choices and decisions.
Detach yourself from the outcome. I heard former NBA Coach Phil Jackson once say, "Don't let success go to your head and don't let failure go to your heart. (Nobody gets everything they want!) In the end everything happens for the best. I personally have had dissapointments which led me down another path which caused me to do whatever and led to a joyful experience. One day you look back and say, "If (blank) had not happen I would have never did (blank) which led me to...etc
Self-confidence comes with building on minor successes gradually overtime. Between my hubs and my book you will find more of my ideas on this subject.
It's your life. Take the wheel!