When couples start to repair things, sex is the last element to return to the relationship. When one or both members of a pair are troubled with depression or stress then sex becomes almost impossible. A second generalization is that men are quite willing to accept all of the responsibility for failure to get an erection. A more useful answer can be found by tracking the interaction between a man and woman. We look for behaviors that facilitate or impede the growth of intimacy.
Women learn early in life how to turn men off.
If they are tired, stressed or just plain uninterested in sex, most women know how to put a quick end to sexual overtures. Men also know how to do this with a partner who is more sexually active than they are. The world is full of men and woman who feel inadequate about their sexual ability. More often than not it is the partner who is turning them off in some subtle way. As always, the first step is open, intimate discussion.