I've noticed that the thing with calm people is this. They are very calm for some situations. But yet somehow, they meet a situation in which they flat out lose it, perhaps from build up. Examples of these people are Lan and Moraine from "the wheel of time", austin fraser from "the underpainter", Spock from Star Trek and Ulquiorra Cifer from Bleach. Is there a reason why people who don't show a lot of emotion, are capable of so much emotion?
Maybe because irritation and anger grows and grows until it pops. Could also be a self-defensive mechanism of the organism, if it grows too long and too much it would cause massive damage, mentally and even physically. Also maybe incapability of self-control in a too heated situation. Some people have "rules", if someone crosses them severely it might be too much to handle. Also the mood they were in before a situation could affect a lot, acting as a multiplier. I myself am very calm, I also have "rules", and the mood I am in at any moment changes my behavior. I find it easy to control myself, but if my mood is already bad and I also meet a bad situation, I could snap at others easily and severely. Calm people aren't really calm at all, they show very little physically, but their heads are constantly full of thoughts, emotions. They are capable for a lot more than those who are normally considered as emotional.
Also, what might be seen as 'calm' is actually just not showing emotions. I come from a family where showing emotions is, well, not frowned on but it just isn't done. If something extreme happens, then it's 'justified', but otherwise being emotional is for 'private times'.
