Does passion come from your writing or arise from your writing?
I have worked with writers who were entirely passionate about the writing project they were about to set out on. The passion fueled their writing and kept them going, especially during those times that every writer experiences where the writing simply is not (definitely not) flowing. The topic was so inspiring to the person that they would find ways around or through the writing obstacles. I have not yet seen a passionate writer I've worked with give up on their project. Of course, I have been working with them as a writing coach and so the process of working with a coach likely was helping them keep up their momentum.
We typically think that we need to be passionate in order to write. Nor would I deny that it helps a great deal. But, I have also seen instances where passion emerges from the writing process. This is an interesting phenomenon. It's as if the more the person writes, the more passion grows. I liken it to the slow growth of genuine love in a relationship. What we often go into a relationship with is excitement. You can call it passion. Many do. But, over time, if the relationship continues and grows a deep love evolves. Also, without an initial passion, often over time a deep love can grow. Over time passion represents far more than excitement. In fact, the first definition of passion in the online "freedictionary" is "a strong emotion, such as love."
Often when we are writing, the piece eventually takes on a form that we can embrace. And we become "passionate" about it. Typically by writing what we know, and sticking with the process, having an image of the outcome we want, the writing evolves into a coherent heartfelt product.
Initial passion can definitely move the writing along. But passion need not be there in the beginning. It is probably helpful to take on a project that at least has some interest for you. You need not be passionate about it as long as you're sure that you write, write, and write some more. This gives the opportunity for the passion to emerge.