Feelings of Emptiness and Dreams when without a model

Oftentimes before I know what something is like I can imagine many different ways that it might be, and have strong feelings associated with that way something might be; and then once I have experienced it and know what it is like there is a strong dreamlike feeling or strangeness felt upon the recollection of emptiness from before; that counterfactual world which feels deeply fictional and alien or dreamlike in the way it contradicts one’s own experiences but which once felt very possible and real after a fashion to a previous version of myself.

I can’t find this precise experience previously discussed.