You are cheerfully happy as you have achieved something great, say a small goal which you had set for yourself. You want to share your happiness with others. Just when you're about to share it, a thought strikes your mind really hard, "What if people don't like my work?", "What if people......?" "What if.......?"
Your "what if" is the one who is holding you aback. Further, this feeling may push you so deep that you start doubting your abilities, doubting whether you're good enough or not, doubting your worth, and you end up feeling discouraged and dishearted.
It doesn't matter whether people like you or your work, people judge you anyway. What matters the most is what you think of yourself, what you think about your work and your abilities. If it's positive, then no power in this world can stop you from achieving your goals. However, if it's negative, the profound feeling of worthlessness in you may mould all your other thoughts into demons which is only disasterous for you.
I agree that these sudden "What if"feelings are inevitable since we're all humans and humans are bound to feel this way. But we should not let these feelings take over us and push us in a state of delirium.
You may believe that you have nothing in you, absolutely no skills or talents. What you do not know is that your talent is hiding in it's den at the moment, ready to pounce when you least expect it to. When you think you are capable of more, your true talent will automatically unfold when the right time approaches. All you need is patience.
I know it's very easy to say, but when it comes to practicing what you preach, things get out of your reach. Just believe in yourself for once, and you will see the difference.
Strongly believing in yourself is the only way you can overcome these "what if" feelings, because if you don't believe in yourself and your abilities, you can never achieve what you are truly capable of, and there's no point in having any goals at all. You are the only one who is holding your self aback, and you need to loosen your tight grasp on your self, release all your insecurities and that day will mark the embarkment of your journey to achieve your goals.