Tears of Joy?

Today was my first grade son's last day of school. Every year my son's school is filled with parents who line the walkway and blow bubbles for the kids on the last day of school. I went and my younger son blew the bubbles. When I saw my son walk out of the building and come toward me, I could feel my eyes start to tear up. It surprised me. I don't usually get emotional like that. Maybe it wasn't tears of joy. Maybe it tears over the realization that school is really over.