I personally find that forcing yourself into a public setting is a great way to gain self-confidence. The “fear of being in the spotlight” tends to be at the root of most people’s insecurities, and a good first step is to practice the art of speaking in front of a crowd. Almost every city has a Toastmasters or similar organization that can offer valuable experience. Many social organizations have structures that allow for terrific training by presenting to groups. If progressing in your work environment necessitates making presentations, I would encourage discussing your fears with your boss and asking for opportunities to work through them, perhaps doing presentations to less-intimidating groups of coworkers before working your way up. The only way to conquer your insecurities is to confront them.
And the fact is that you own your insecurities, and it is up to you to learn to deal with them. Unfortunately, it is easy to let insecurities rule your life and then, when you don’t achieve your dreams, start whining about injustice.