It is a widely studied fact that olfactory memory is one of the strongest types of memory in human beings. (This is the part where I would reference studies to you right now, but since I'm not a college student nor a pompous ass I won't.) I have found this to be abundantly true in my own life.
A perfect example is the memory about Italy I wrote about just the other day, which was brought on by the smell of a beer. One whiff and it wasn't just a memory, but a feeling that was recalled to my mind.
Another very particular smell reminds me of a certain girl and certain things we used to do to each other years ago, and when I smell that smell; her smell, it drives me crazy.
And just now walking into my barracks room I smelled another. The smell of fall that comes through a window left open at night when its just a little too late in the season for windows to be left open. I don't know how that smell found itself all the way down into this hellish desert, but I'm glad it did.
It makes me think of waking up late at night when I was in middle school and lying with my head as close to the window as I could get it until I fell back asleep. It makes me think of coming back from college to find that my house wasn't Home anymore, and even my room wasn't My Room anymore. It makes me think of getting home late from work at the restaurant and sitting on my bed feeling cold and tired and alone, confused by everything that had happened.
I know those memories might not seem like very fond ones but they're strangely comforting. I don't really know why.