Being a person who finds tears arising in all manner of situations, I was naturally drawn to this piece by Frederick Buechner, which I found on Tim Keel's blog (unfortunately he doesn't tell us where it comes from.)
"You never know what may cause them. The sight of the Atlantic Ocean can do it, or a piece of music, or a face you've never seen before. A pair of somebody's old shoes can do it...You can never be sure. But of this you can be sure. Whenever you find tears in your eyes, especially unexpected tears, it is well to pay the closest attention. They are not only telling you something about the secret of who you are, but more often than not God is speaking to you through them of the mystery of where you have come from and is summoning you to where, if your soul is to be saved, you should go next."
Substitute the Pacific Ocean for the Atlantic or a photograph of my now deceased mother holding one of my sleeping grandchildren as a tiny baby for the old shoes, or a sloppy movie (in fact, not it doesn't even have to be sloppy) for the piece of music (not that I never get emotional about music), and you have a picture of what might cause me to be emotional any place any time.