It is real and affects different people in different ways (which is an obvious statement really but there we go). Some people, because of their personality, can cope with stress very well whilst others go under at what seems to an outsider the slightest thing.
I've worked with people who, after a period off work with stress, have not been able to cope back in the classroom and have had to take ill health retirement and others who, under the same amount of stress thrive on it. It is not something you can really measure, IMHO, it is individual. I remember when I was training there was a quote that went something like; "everyone is an individual with an individuals needs and an individual fingerprint. No one person is the same as me".
So yes stress might be a Messerschmidt etc., but it is also a pin prick in your thumb or a child who tells you that they are not going to wear the clothes you want them to wear. (because that could be the last straw!) In other words you can cope for so long then wham it all catches up on you. I know, I've been there.
Sometimes the Messerschmidt is easier to cope with actually. There's nowt so queer as folk as my old Gran used to say.