Shrinkage!
Significant shrinkage !!
Drugs or alcohol will inhibit erections.
And consumption of sugar also inhibits erectile function (I read a few years back that alcohol has a lot of sugar in it as well).
And basically, the same sleep habits, exercise and diet recommendations to avoid cancer, hypertension, diabetes, heart disease and weight gain, are all the same things that will improve your ability to get your little friend hard as well.