Can’t work on my work until my ‘paid work’ is done

I am trying to wrap my head around this thing that I do a lot and need some insight.

I always tell myself that once I finish my real work for the job that pays me then I can do my other work, which is working on my book, and work on my own side business (which doesn’t pay me money yet).

I want to create time to work on my own things in addition to that “paid work.” I feel a lot of pressure from my boss to work all hours of the day, and when I do sit down to do my work I’m anticipating a text/email that he needs me to work on his project. So, I tend to just keep working on that until I feel caught up enough (which doesn’t often happen) before I can focus on my own work.

So here is my UM

C- work on work emails at 9:30pm Sunday
T- once I’m done with work then I can do my “other work” (writing/my own business)
F- stress
A- work on “paid work,” clean, do laundry (other “necessary tasks” in my head)
R- I never finish “work” and so I never do my “other work”

I understand that my results are caused because I’m thinking this T. I see that I never actually finish work and then I create the situation that I have no time to do my other work.

But I don’t know how to change that or get to a point of actually realizing it.