As stage manager, I was always the first and the last person on stage. Working on tour can be stressful as you have to keep track of where everyone is for health and safety reasons and monitor everything that goes on backstage and keep to time. Then once the show is over, you have to clear everything and make a note of everything that needs repairing or redoing before the next performance.
The completed text describes the role and responsibilities of a stage manager in the context of a theatrical production or performance.
"As stage manager, I was always the first and the last person on stage." This suggests that the stage manager is responsible for being present at the beginning and end of the performance, likely to ensure everything is set up before the show and to oversee the closing procedures.