Old memories of loss can be stirred up, making it hard to be sure if we're missing the person who just left, or someone else. Talking with a parent, a friend or a counselor often gets fear under control. Don't let it keep you in a bad relationship. This emotion lets us know that we don't like the treatment we got. It doesn't necessarily mean we are right, but it's our emotional protest.
Anger can be healthy or it can be dangerous.
It's like fire. It depends on what you do with it. Grief is the sadness that goes with missing someone. Sometimes grief hits instantly. Sometimes it comes even before a break-up if you know the split is coming.