There are few more demoralizing things than running as fast as you can through two large airport terminals (on a bad knee) to make a connecting flight departing in 25 minutes, speed through security and immigration, and arrive just in time to see your plane depart through the glass window. A plane that was apparently notified of your delayed arrival because both flights were run by the same airline.
One thing more depressing might be doing all that rushing and actually arriving 15 minutes before your plane departs, but being told they already sold your ticket.
I'm stuck in Frankfurt. See you tomorrow San Francisco.