Where to begin?

The desire to just write a book of a piece oh lord 

I‘ve heard so often from teachers who graded my assignments that I should become a writer. And I have loved the reactions of readers to my pieces - that rollercoaster of many emotions, where you‘re not quite sure whether to laugh or cry, or do both at once. My writing doesn‘t have just one mood; It‘s written in a very fluid way. Just as life feels to me - not fixed but flowing.

The thought that I can capture everything dear to me on paper, that I can make a piece of my heart tangible … oh, how awesome

I don’t know where to start or how. So many ideas are swirling in my head. Has anyone here ever written a book or a piece? How did you manage to do it?