Only when it's wrong
I can't maintain an erection unless I'm having "forbidden" s** of some sort. I can get - and stay - hard as a rock when I'm f****** a married woman, or a woman who's got a boyfriend or a fiancé. I can plow my friend's ex-wife with no problem. I can hold a raging b**** when another man is sucking my d***. If I'm with a single girl who hasn't been married to one of my good friends I lose the erection within a couple of minutes. My mind only wants s** when I shouldn't be having it.