One way to understand the troubling reactions that follow a traumatic experience is to think of them as emotional pain. These reactions, which might include changes in emotions, thoughts, and physical sensations, all stem from the normal working of the brain/body system and function as part of the healing process in a way that is similar to the role of physical pain following an injury.
When we suffer a physical wound, the brain and body responds with pain, redness, heat, and swelling. These symptoms show that your system has increased blood flow, fluids, and white blood cells to the affected areas to begin the process of healing. The pain alerts you, letting you know there's a problem, enabling you to assess the situation and protect yourself from further injury. Your body then repairs itself and gradually returns to normal functioning. However, things can go wrong sometimes, and the inflammatory response can fail to shut down at the appropriate time. Unresolved inflammation can cause damage throughout the body and the continuing pain becomes a problem instead of serving its purpose.
A similar process of crisis response occurs when your wellbeing is severely threatened. Your brain/body system detects the danger and responds automatically and instantly to protect you. This happens in a fraction of a second, without your conscious awareness or control. Adrenaline and cortisol pump into your bloodstream, giving you energy, increasing your alertness, sharpening your senses, and speeding up your heart rate and breathing - all to enable you to spring into action and escape the danger by fight or flight. When the situation is resolved, your system returns to normal functioning.
Unfortunately, just as physical healing can go awry, so can emotional healing. Your system can become stuck in crisis mode and respond to normal, daily situations as though they were emergencies. The energy required for the emergency response takes a toll on your system, and the chemicals released throughout your body can negatively affect your sleep, attention, mood, thought process, and physical health. The good new is that you don't have to stay stuck there forever. Equipped with knowledge, courage, and perseverance, you can calm and retrain your system to get your healing back on track.
I hope that this metaphor of trauma as emotional pain is helpful to you. It provides just one view of the enormous topic of trauma, but hopefully can serve as a reminder that the trauma reaction is a natural process intended for your wellbeing. When problems arise, they can be resolved and health restored.