Emotional and psychological traumas happen to everyone. It can be caused by a one time event, ongoing relentless stress or commonly overlooked events such as break-up/divorce, surgery, humiliating or disappointing experience.
Not talking about your trauma will not make it go away. The more you push it down and try to forget about it, the more it will try to come up and remind you that it exists. It comes up as nightmares, flashbacks, anxiety, panic attacks, anger, sadness, uncontrolled emotions and other unhealthy ego defenses. It has different ways of reminding you that it is unresolved and it needs to be processed.