All that you can't leave behind

How do i explain this?
I have these moments where i feel an intense longing for Sydney. One time, i was in church and (suddenly) saw myself on the train going towards Town Hall- above me the Harbour Bridge and to my left, the Opera House. Another time, i was crossing the road when i felt a (sudden) rush of memories of Sydney take over my entire body- the little things like drinking coffee and wearing a jacket and also the big things like my Aussie family and Justin. Just now, i was reading when an image of Bondi Beach came (suddenly) to mind and i could almost smell the beach and feel the cold water against my bare skin.

These moments are overwhelming. They make me feel joyful and secure and sad and fragile all at once. A plethora of emotions run through my veins and it's all i can do not to fall over.