I cannot be sure, because we have no context. However, from what I understand, the first sentence is an example of a transition sentence for your second body paragraph. It basically is saying that people hide their emotions and feelings.
The prompt is telling you to explain why people would do so.
Since the prompt is to write about why people choose to hide their true emotions, maybe you can first elaborate on <em>what</em> these people are feeling (if you are doing this on a specific topic) and how it's possible they don't want to show their feelings in fear of feeling exposed and vulnerable. Perhaps people don't show others what they're feeling because it's a privilege they aren't ready to share with certain people.
This is really about your interpretation, so it's important that you use what you know about humans and logic. I just gave an example, but you will have to write more on it and explain it in detail if you choose to use it.
