Every single of us has a set point for happiness.
It's a cealing, different for everyone and related to our sense of worthyness, based on which we allow happiness to come in.
When happiness crosses that line and we get unexpectatly more than what we allow to, we unconsciously make something happen to ruin that extra amount of happiness and abudance. It's called Upper Limit by Gay Hendrix. It's real. It's unconscious and it's adjustable.