So, can you restrain your emotions?
Can you look like a cold hearted bastard on the outside, but on the inside you're burning with fury, sadness, love, jealousy, rage, a desire for revenge, companionship, loneliness? Or do you simply let it all out, not lying to anyone or yourself.
Also, here is a commonly known hint - if you don't show anyone your feelings, they won't know how to hurt you (along the lines of something like that). Make your weakness your strength.
I actually don't get why people can't hold their emotions in. What's so hard about it? Is it something that is just that uncontrollable? I'm also going to be stereotypical here, but I'm guessing the majority of the people who posted on this thread about how they can't control their emotions are women/girls. Just hold the -blam!-ing emotions in, that's what makes you strong. (I already posted how I find it too easy to hold my emotions in, along with that they should be held in. This just came to mind, though.)