When I was growing up, I spent many days in the summer with my grandmother while my mother was at work. I spent many nights with her, too. Being a typical young boy, I often found my way into trouble.
My grandmother had a way of frightening me into obedience without lifting a finger. The power of her words and gesticulations as she served up a warning to "behave or else..." was amazing. All she had to do was tell me that some evil spirit was waiting around the corner for me the next time I misbehaved to swoop down and scratch my eyes out.
It worked on me. I remember many of her warnings to this day - stuck in my brain. As a freewriting exercise, write about what frightens you. Make it a little more interesting and write about what has frightened you at different times in your life.
The idea of evil spirits are still scary, but at this stage of life, other things frighten me more: losing my little girl in a crowd of people, or the love of my life, for example.
What frightens you? Place yourself in that scene. Use your five senses as you write.