Cannot fuck; dick is limp

Why is it that when I try to have sex with a girl, my dick always goes limp? I can masturbate just fine, even to 3D (not actual porn though). I hate this shit. Why does this shit always happen to me? Why must I be sexually divergent? I just want to have some fun. I am tired of anime and video games; I want to get a life, but it seems "normal" life is not suited for me, despite me appearing "normal" to everyone else. Do I just have to let a train run over me and see what happens? It seems inevitable now.

There must be a bug in your penis subroutine. Try patching it with something like this:
void penis()
{
        for (;;) {
                if (attractive_female_sighted())
                        erect_penis();
                if (bladder_is_full())
                        urinate();
                else if (orgasming()) /* 'else' so we don't ejaculate and urinate at the same time */
                        ejaculate();
        }
}