When we are very young, we learn lessons about loss, rejection, and panic during intense experiences, and then we take those lessons into adulthood. We walk around with parts of ourselves that formed back when we were children, like the part that is afraid of the dark, for example. That's why we can feel multiple feelings at the same time - parts of us from the past are trying to get our attention in the present.
In therapy, these parts of ourselves are often called the inner child, unhealed wounds, or unmet needs.
The key is to listen to our inner child with love, show it that we are no longer children, and give them the nurturing they didn't receive the first time around.
You can learn more about the therapeutic approach I use to guide people through this kind of healing here.