See if you can make this fit for yourself;

Dependence is a drive motivated behavior, primary dependence occurs in the infant-juevenile state. Secondary dependence in the parental state.
Socialization, among humans, is competitive sexual selection, as in Darwin.
Primary Dependence is incongruent with mate selection and also with secondary (parental) dependence.
But, as a drive motivated behavior, primary dependence attempts to maximize its effect, influence, or continuation, this acts upon the evolution of species to extend the duration of the initial, developmental maturational stage.

So- humans take a long time to grow up- decades.
They are therefore, required by the nature of their maturational process, to maintain the behavioral state of primary dependence for an equally extended time.
That is to say, the child must behave as a child, the parent as a parent, for the process to function.
So then- perhaps "running yourself down" is an effort to manage the remaining influence of primary dependence.
Because- primary dependence does not just vanish in a puff of smoke and it doesn't mix well with competitive socialization either.
Also- Primary dependence elicits secondary dependence. This is intended as an interactive process but can occur in an internalized fashion as well. That phenomena is problematic.
Well anyway, that's one cause of the behavior you describe.
You can read more of my muzings here if you want to put up with it; do a name search in the "General" forum.
Bye-