The last reason is an emotional maturity. An emotional maturity is an indication that you are in any age. It can observe easily, especially when you are angry. If you show your emotion through the facial expression, that means you are still a child. In contrast, if you can hold your emotion, that means you become an adult. I believe, people at the age of 23 years are able to manage their own emotion well because they have a lot of experience in the university. It help them can control themselves. Whatever the situation, they know how they should show emotion.