Basically, it’s just anxiety.
When we’re babies, we’re emotional and full of fears and rage and we scream a lot: We’re hungry, our diapers are wet, etc. Our parents discipline us and tell us to get a hold of our emotions (“Don’t be such a baby!”). They tell us to put our emotions on hold, at least until we have looked at things logically for a reasonable explanation or resolution.
But later in life as adults, our childish fears or strong emotions sometimes break free despite us. Then we feel the punishing scorn of our parents all over again, even after the parents are long gone.
Strong childish emotions (especially counterproductive ones like anger and fear) get buried in the unconscious id along with a lot of other childish stuff. The old parental discipline turns into our superego, which acts as a lid on the id and keeps it from breaking free. But occasionally snippets of the id escape under stress. Eventually the superego kicks in again, tamps the id back down, and re-establishes order. But as a result of the activity of the superego we outwardly relive the anxiety at the parental discipline that went into establishing the superego. Ultimately it all goes away when the id quiets down again and the superego doesn’t have to strain to keep the id bottled up.