I have just finished reading The Art Of War For Writers by James Scott Bell. And I found it to be a good book to have regardless of what stage of your writing you are at in your life. Whether you are a beginner or a professional writer, it doesn't matter. He explains everyday scenarios very well and I personally learned a lot of new things too.
He tells you plainly what life as a professional writer is like and he even talks about how to survive and prosper as an aspiring writer. In my personal opinion I think it is a must have, especially if you are anything like me. I constantly feel lost in this whole journey of trying to get published and some days I just don't know how to handle certain problems.
Just thought I should share this.