Neither Einstein, Galileo, Leonardo Da Vinci Socrates, Elvis, Maradona or your Kardashian of choice, could have individually permeated our consciousness to inspire or disgust the masses without the ability to communicate their message.
So many smart, creative and ambitious individuals fall short in the attainment of their deepest desires, as a result of self doubt. The fear of being wrong, and the consequent ridicule that may follow, results in too many dreamers stepping back from the edge of potential greatness.
If for example you are applying for a job, I'd suggest being bold and assertive. This of course does not guarantee you an interview but it is imperative that you be noticed, for the right reasons. What is right of course is arbitrary, however it is indeed a rare interviewer who won't admire unashamed passion and hunger to be heard.
Lack of confidence suggest a sense of not feeling worthy, somehow portraying ourselves as less than adequate. We may have plenty of references in our life to justify our feelings of inadequacy, such as historical mishaps, and the echo of parental or peer undermining commentary, however they are WRONG
When hopefully you have that epiphany that it really is OK to be you, your interaction with the world changes. There is no reason to apologise for any perceived personal flaws or communicate any sense of inferiority to anyone. If applying for a job, or a business loan, or a potential romantic coupling, communicate with 100% conviction. Imagine you are the best, project yourself with sincere and earnest intention.
Sub consciously we can default in our communication to some zone between confidence, ambivalence and indifference. Fake it until you make it. Confidence is a habit, but there is a high price to pay for appearing ambivalent or indifferent in any form of long term relationship building. Believe that you are indeed worthy of being heard and express yourself
Incidentally, 99% of all your ancestors thought the world was flat, and a thousand other obvious truths. They were wrong - be less worried about whether your vision is right or wrong in the eyes of the masses, run with your convictions and be heard.