We’ve been interviewing peer ministry candidates this week. We invite each candidate to lead prayer at the beginning.
Catholics naturally open prayers with the sign of the cross. But lately, I’ve been declining to close it off with a similar sign. Why segregate prayer? Pray at all times. I’m thinking it’s time to stop ending prayer. Better to just keep it going.
Besides, it’s finals week in my university city. Those students need all the help they can get the next few days.
Catholic Sensibility 
Or perhaps you could think of the sign of the cross at the “end” as signifying you are going forth in prayer.