“How do I not live in fear after being in a foster home and seeing terrible things?”

I will suggest you follow up with a therapist that will work with you in navigating these fears, and identify positive coping skills.

If you grew up in the foster system chances are you suffered from a variety times of trauma as a child/adolescent. I hope that the cycles didn’t continue in foster care, but unfortunately I know they do. Fear can be a normal human emotion. However, it terms of fear related to trauma it can cause impairment in everyday function. A part of overcoming trauma is learning to accept the past. But it doesn’t have to be the future. There are plenty of good people in the world. Don’t be afraid of finding them!

I would suggest seeking therapy, particularly aimied at trauma. DBT therapy is one excellent form of therapy for trauma victims.

I would encourage you to practice loving kindness, patience, and being mindful. Your past does not have to define your future. Professional counseling is an option as well.
Have a blessed day.

You describe the symptoms of Post Traumatic Stress Disorder (PTSD). You (obviously) do not describe how "Living in fear" impacts your daily activities of living. You should consider meeting with a licensed professional counsellor who can help your describe the terrible things you saw and talk you through your fears. Very often, recalling each specific terrible event in a safe environment will help the fear go away. I must add that what you describe is not the same as the PTSD that military personnel experience from events on the battlefield or serving in peace keeping operations. For them, the resolution is much harder.