I lost most of my ability to have full and spontaneous erections after my prostate removal. The advice from the Dr was use it or watch it shrink. It is possible to damage the penis when attempting penetration with an insufficiently erect member--Google Peyronie's disease. Post-prostatectomy patients are prescribed a low daily dose of Cialis to improve blood flow, since we may no longer have the nocturnal tumescence (morning wood) necessary to provide blood flow to the erectile tissues. Options for continuing penetrative sex include Cialis and Viagra, a pump, and, the nuclear option, injections of bimix and trimix, which can literally raise the dead.
For my wife and I? Meh. Good riddance.