Fear is a funny thing and presents itself in odd ways. When we think of fiction, we imagine fear to present itself in dramatic ways along the lines of PTSD—hypervigilance, panic attacks, explosive temper, stockpiling weapons in the house, etc. But that type of thinking is fairly limiting, especially for writers of genres that don't include stalkers, wars, or murder mysteries. Everyone is afraid of something and it is not necessarily violence. Regardless of that fear—big or small—it manifests itself in a person. The question for you as an author is how will that fear manifest itself in your character.
Here's an example from my own life, one that still astounds me. This time last year, I was thin and fit. I worked out four times a week and, though I wasn't on a diet per se, I was mindful to watch my intake of sweets. Then, one night, I woke up from a deep sleep covered in sweat. I was shaking, nauseated, yet desperately hungry. When I got out of bed, I was so dizzy I could barely walk. I didn't know what was happening to me, but I knew I had to eat. NOW. So I stumbled downstairs, heart racing, and shoved every bit of easily digestible food I could find into my mouth.
Similar to a panic attack, that bout of low blood sugar was a terrifying episode during which I was quite sure my own death was imminent. My doctor calmly told me that as a hypoglycemic person, I just needed to make sure I was eating regularly and to monitor how I felt. "Listen to your body," she said. But I didn't. I listened to my fear. So every time I felt even a twinge of hunger, I would reach for food, usually terrible food like a candy bar. As a person who exercised, that couldn't hurt, right? I was so scared of waking up with a sugar attack again, I made sure I always had food near me.
Fast forward a year and I have put on 50 pounds. That's right. 50 pounds. In less than a year. The good news is, I'm getting it under control. But ultimately, fear made me fat. And I'm not the only one.
It only takes a few episodes of watching Iyanla, Fix My Life, on the Oprah Network to realize that fear makes a lot of people fat. People who were victims of sexual abuse or assault as children often put on massive amounts of weight in adulthood to keep people away from them. Gastric Bypass patients often put all of their weight back on, and then some. Is this because of a self-control issue? Of course not. Their stomach is the size of a grape. Eating large quantities of food is unappealing. But they do it anyway. Why? Because in their heads, they're still "The Fat Girl" or the "Fat Guy." They got that way for a reason—a deep-seated fear that manifests itself in their bodies.
As authors, we all know that damaged people are the most interesting to write about.
Despite that damage, many authors imbue their characters with Mary-Sue-like good looks. It's a missed opportunity, in my opinion. Only about 1% of the population is naturally beautiful (as in without makeup, hair styling, or fashion sense), if that. So if your character is beautiful, they probably have to work at it.
What drives them to invest so heavily in their appearance? To go to the gym, to buy all that makeup, to watch what they eat, to go through that five-step facial cleansing routine? What fear are they chasing away at the beauty counter?
And if your character is not perfectly beautiful? Do they dress outlandishly like Lisbeth Salander to ward off people because of abuse? Do they wear oversized clothing or have poor posture in an attempt to be invisible?
Knowing your characters inside and out is part of writing a story and fears are an important part of the puzzle. For better or worse, we all wear our fears on the outside where people can see them, if they know where to look. That truth should be reflected in your characters.