You've been carrying something for a long time. Maybe it's a single event that shattered your sense of safety. Maybe it's years of smaller things that accumulated until you stopped trusting your own perceptions.
You might notice that your nervous system has a hair trigger. A tone of voice, a smell, a situation that resembles something from your past, and suddenly you're flooded with feelings that don't match the present moment. Or maybe you've gone numb. You don't feel much of anything, and you're not sure when that started.
You might have done therapy before and talked about what happened, maybe many times. It helped you understand it. But understanding hasn't changed how your body reacts. The memory still has charge. The patterns it created are still running.
You're not broken. Your nervous system is doing exactly what it learned to do to keep you safe. The problem is that it's still running a program designed for a situation that's over.