People with trauma and stress disorders can react to feelings of abandonment more intensely than others. As feelings of past abandonment trigger memories of those traumatic experiences, like childhood neglect or abuse, these changes can lead to flashbacks, nightmares, and intense emotional struggles.  The past trauma can make them revert to more active levels of hypervigilant looking for signs of rejection. A perceived slight can trigger a fear of being abandoned, leading to anxiety and panic attacks or even worse. 

Those that have these disorders have a very hard time trusting others, which can make it hard to form those important relationships. Feeling abandoned seems to reinforce their belief that people are unreliable and everyone will eventually leave them. These re-traumatizations may send them down a spiral of unhealthy coping mechanisms to deal with abandonment, like self-harm, substance abuse, or isolating themselves even more. 

You may find them becoming angry at the person they feel abandoned by, even if the situation doesn't warrant it, because it is easier to get mad and push people further away than have it taken away a little bit at a time. They might become clingy and possessive of you or possessions that are associated with the relationship due to the fear of being left behind. They might act desperately to avoid abandonment, even if it means sacrificing their own needs, or doing something you wouldn't expect. This could include withdrawing from social interaction altogether to avoid the risk of further rejection.

If you or someone you know struggles with trauma and abandonment fears, it's important to seek professional help. A therapist can help develop healthy coping mechanisms and address the underlying trauma. These people can be smiling one day and gone the next and the same thing we always hear is, "I didn't know."