At the start writing a book seems such a daunting task, like thinking of climbing mount Everest.
I sit at my table with my laptop and a piece of paper, and think this piece of paper will be the starting point of my latest novel. Many weeks later 1 page has become 350 pages.
My advice is, everyone has a story so do something about it and start writing. I have had knockback after knockback from publishers, never give up on your dream.
Go out there and show the world you can write and have a story to tell.