You cannot think with an "expert's mind." You must always be a student, for if you think only with an experts mindset, you will not be open to new possibilities and ways of thinking. No matter how much you learn and grow, you must always keep your beginners mindset.
In the words of my zen masta:
“If your mind is empty, it is always ready for anything, it is open to everything. In the beginner's mind there are many possibilities, but in the expert's mind there are few.”
- Shunryu Suzuki