[Eren is fortunate (in ways) to have retained his memories after returning home. The same isn't true for Reiner. It's really something that he'll have to experience for himself in order to understand. Eren's sure it will only be a matter of time.]

It's difficult to predict. Whoever controls this place [Eren isn't necessarily convinced that it's only Vaeros, at this point - it's been that way for a while now.] has the ability to influence our minds, interfere with our memories, our perceptions...