Writing in your head

When you think about it, you are doing writing all of the time in your head. I think to myself all of the time but when it comes to writing it down it is always a jumble of words that make no sense. For some reason when I am asked to turn my thoughts into a paper I freeze up and think "I cant do this, I suck at writing" and just with that I discredit myself and mentally convince myself that i am not able to do well with the assignment. I do not know why this thought happens and I know people are out there making millions of dollars by becoming published authors. I just guess that these people have embraced skills and put them out there openly not caring what others think. They have conquered their alter ego and let their words flow. This is only something I hope to do slightly to get by. I will never be that published writer type but I will try my best not to physic my self out over these papers anymore. Mental validation is the down fall of many people and thus we have to try to make ourselves stronger to overcome these metal challenges.