I think a lot of people here offered some things to explore. Definitely, this is a perfect topic for therapy. A really important one!

I do think, as one person mentioned, that individuals are born with certain tendencies. Whether or not they equate to a disorder, or are just general personality traits, I'm not sure. I also think upbringing can play a role. Have you studied a bit of psychology in school? If so, you may recall "nature vs. nurture". How we feel, think, act, etc, is influenced by both.

If you feel that any level of emotional immaturity affects your life negatively, it would be good to work on growth. I definitely think such growth is more than possible. That doesn't mean you have to be "tough as nails" or stop enjoying cartoons, if you still like them, but do continue to grow.