I found this was a problem with Tevo and my HF novel, Wolf. My Tevo world was really getting me excited, I was finding plot ideas, I even started writing about it. I realised then that I was leaving my HF novel behind because of this.
I think it depends which is more important to you. I am not stopping my world building, it just slowed down. It's not going to be my main focus until I have finished my HF novel, because that is what is more important to me right now.
Some people find they manage writing two stories at once. It's down to the individual in some ways, I think. However, basically what I decided was that my HF writing came first, so Tevo is worked on in my free time; my HF writing is done in the mornings and afternoons on days when I have no dogs in to groom. So it becomes my work almost. Tevo at present is done in my relaxation time. When my HF writing is finished I can decide if I want to focus on Tevo as my next story.
Hope this helped a little!
