Why is it always like this?

I always have something to say but never feel up to it, and even though I try, I can't get all my thoughts onto paper! I try and try and try but It never comes out how I want it to sound. I could sit starring at the screen and still the only thing that I can think of to say would be... 'I don't have much to say, soooo Hi.' and, let's face it people, we all know I always have something to say.
Got any helpful advice??