Well, we can’t do it for you; for one, it’s your story, and two, we don't know what’s happening in your story.
I can tell you that in order to have a good character; you might want to think about their personality. Then come up with a weakness, or fault, and have a good reason for it.
The time the character spends in your story should be building on their weakness. Then
towards the end of your fictional, have the main character face something that confronts with his or her fear. The outcome is up to you. Just because you are writing about something that typically has happy endings, does not meant that your story has to have one.
Bottom line: when thinking about the character, make sure that you think things through: how their personality might change in the story. How their weakness will affect their actions, and their emotions.
Try to make the character as life like as possible, it will make your story seems more believable