The complete phrase is: WHAT YOU SEE REFLECTS WHAT YOU THINK, AND WHAT YOU THINK IS NOTHING BUT A REFLECTION OF WHAT YOU WANT TO SEE.
We can say that in the first part of the phrase, the important word is "think," since what I see is a reflection of what I think. In the second part, the important word is "want," since what I want is what I think. Let's change the word "want" to "will."
Wanting implies not having, and that is impossible. If we look for a better word, it could be "desire." While it positions us from a different place, it still doesn't suffice. But the word "will" is something else entirely. "Thy will be done" doesn't say what you want, nor what you desire.
Do we act according to what the Course teaches us?
Many people say: I don't know what I want, but I know what I don't want. What is the reason you think about what you don't want? It doesn't make sense. I think about what my will is. Remember that where your treasure is, there your heart will be also. Put your thoughts in order and consider what your true will is, focusing on what you desire and what you don't. This is an important step.