An Original Idea?

For anything I really want to write, I get stuck. Many people just say that you can write what first comes into your mind. How can i do so if there is so much things going around? Normally I think all my ideas are not original and they are mostly based of what Ive seen or heard, not entirley by me. Its just so frustrating! They just told us about publishing a blog and write anything. I find myself wiriting this which sounds really stupid. Maybe I should just wait until a great idea pops out and I may think what to write about. For now, I will just publish this plain writing.