Turns out the impotence craze and all the attention given to the problem trying to create the new viagra has shown that men who can't get it up may not be pumping properly in two ways. [link]

"If you turn on your kitchen faucet and you don't get any flow, either the faucet's broken or the pipes are clogged."

So tell your wife the reason you can't get it up isn't because she has sagging breasts and is starting to look like your mother but because your slowly dying. I'm sure that'll make her happy.