Your life is a story. A journey of experiences, both good and bad. You gain wisdom and character from each of those experiences. Tell your story. Write your story.
Whether it is fiction, non-fiction, or whatever the genre, if you have a desire to write a book sit down and start writing. Your first draft will probably be bad, but it lays the foundation for later edits and improvements. When the inspiration is just not there to write, read. Read other books and make mental notes of that authors’ style. Do research on the genre you are writing. Think you are not a good writer? Not good at grammar, spelling? I have that problem too; however, I am working on that, and remember, there are people who are very good at editing. Write your story and let an editor check your work. Enjoy.