When I've got to have a mask on for long periods of time, I can become a bit emotionally unstable. Minor provocations can occasionally result in a crying fit. It doesn't happen very often anymore since I'm taking a break from work; customer service requires a pretty sturdy mask.
Things that have made me cry so far... also frustration at feeling powerless in some circumstances, anger with myself after a fuck up, defeat, intense pain, a few women I cared about...