After reaching the end of the mission it is a good time to celebrate if successful, or to point out team strengths if failed. Whether it was a successful or failed mission, it is always worth it to take a few moments and conduct a debriefing to discuss the finer points of the mission. Have the crew talk about good choices that were made, times they struggled, strategies that could be improved on, and story points that were enjoyed.
Mission completion is usually signified by performing a blackout. With no more visuals or stations to interact with it is easier to hold the crew's full attention.