A familiar smell can bring back forgotten memories with remarkable clarity. For me, listening to a song I have written long ago somehow takes me back to the moment it was written, with all the thoughts and feelings that went into writing it. I am brought back to the porch where I used to sit and listen to the nearby stream, or the roadside stop where I pulled out my Backpacker and wrote the song, and can remember those views again.
You also see just how far you've come from where you were at that time. Like a dusty, tired traveler, you feel the weariness of that long journey, full of its many ecstasies, struggles and pitfalls. You feel the sensation of every step that brought to where you are today.
In a sense, our music is a time capsule of all these moments patched together. You see your soul's journey and how you have been molded in what you've become.