Is it possible to have an impossible goal be two goals?

Or should I practice restraint?

These are two concepts you teach. Right now I have a goal to write book that I’ve just started this month. But my boss just offered me a new position at work that would require a lot more work and new learning. I would have three departments reporting into me, and have the business goals of the company fall under my responsibility. If I really want to excel, I believe I would have to devote additional energy and focus to the new position. My question is should I apply constraint here and choose one of these areas to produce extraordinary results in 2021. Or could an impossible goal be to accomplish two goals: excel in this new role AND write a book?

My initial reaction would be that it would be better to focus, but I’m wondering if I am just using that as an excuse. Thoughts?