Memories, imagination, old sentiments, and associations are more readily reached through the sense of smell than through any other channel.

Smell bypasses the part of you that narrates and goes straight to the part that remembers. A single unexpected scent can return a whole year of your life with a completeness that no photograph manages, including the feelings you had forgotten you had. This is why old houses, particular soaps, and certain kitchens can undo a person without warning.

There is something usable in that. If you want to remember a period well, notice what it smells like while you are in it. And when grief arrives out of nowhere in a shop or a stairwell, it is often this, which makes it less alarming and easier to let pass.