That's funny, because I would call it being an adult and being able to control your emotions.
To be honest, that's actually called being depressed. It's a fairly common defense mechanism, especially if you're being picked on or whatever it is that people do to get you mad.
Sometimes it's really the best option you have for dealing with a situation you can't really control, like school, prison, whatever. But when you're out of that situation you're gonna want to deal with it. It's not something you can just turn on and off at will, and unfortunately the more time you spend in that state the easier it is to sink back into.
I know I'm being a stupid idiot for replying to what may be an off the cuff comment, but for real, depression sucks and the attitude you've expressed makes it sound like you currently are deep in it. So I'd say you'd do yourself a service by trying to find ways to expand your emotional depth. Find a place or a group who you can be comfortable with, and try to let yourself feel the emotions, rather than shoving them down.
And when you're out of the situation you're in talking to a therapist really can do wonders for people. You gotta find the right one, half of them are hippies, but if you don't take care of depression like that it can easily lead into anxiety attacks down the line as that shit you're not dealing with keeps building up.
