A writer is happier when they write. This is reason enough to not be discouraged by the slow growth of a following, fame, or even money. If you are a writer and you stop writing you will be miserable.
I would just say let go of the external expectations around your writing. It does not matter how slowly you grow or how many email subscribers you have after a year.
I think a lot of people stop writing after a year because they are searching for something else. (Getting rich quick, becoming famous fast etc.) I suppose some writers give up because they don’t realize it is worth doing just for their own personal growth and satisfaction.
I understand the pull of all the different things, the way I manage it is to just give everything a little bit. The less it matters to me, the smaller the chunk of time I give it. Marketing does not get much, just a bit. If you want to work on your book, write fewer blog posts. You can blog once a week. You can cross-post from your blog to Medium and you can spend the hours you would have on writing more blogs on the book.
I automate everything I possibly can. Do what is the most important to me, and then let the rest go.
I have six kids whom I homeschool, I have been writing consistently for three years, although I only went online with it one year ago. Before that I was writing curriculum for a homeschool company and a few magazine articles.
I have a total of 2 email subscribers. (I think I started my list about 6 months ago.) I was thrilled for each one. I get excited about every single little forward movement. Why? Why not? I don’t need to have guru numbers to be happy.
When something doesn’t move forward, I rest content in knowing that at least I am having a good time.
I hope this gives you some encouragement.