Nobody can say how an individual will react in a given situation. However, controllers are subject to constant checking whilst at the College and by the competency examiners at their final units. If a controller was heading for some sort of breakdown it would probably become obvious so steps would be taken in good time to prevent a major problem arising. If things did suddenly go awry, the controller would be relieved from his position. I don't recall ever seeing that happen but I knew several who were getting on in years who asked to be posted away as they were finding things difficult.