Passing across a real or virtual threshold erases some of your memories, Scientific American writes:
This “doorway effect” appears to be quite general. It doesn’t seem to matter, for instance, whether the virtual environments are displayed on a 66” flat screen or a 17” CRT. In one study, Radvansky and his colleagues at Notre Dame tested the doorway effect in real rooms in their lab. Sure enough, memory was worse after passing through a doorway than after walking the same distance within a single room.
The doorway effect suggests that there’s more to the remembering than just what you paid attention to, when it happened, and how hard you tried. Radvansky and colleagues propose that walking through a doorway is a good time to purge your “event models” because whatever happened in the old room is likely to become less relevant now that you have changed venues.