Adultery doesn't just happen. The eye can inflame our sinful hearts, and our hearts move our bodies. Jesus was stating in dramatic terms that we must deal radically with sin. He used the picture of maiming to demonstrate how repugnant sin ought to be to us – as much as we are repulsed by the thought of cutting off one of our arms or plucking out an eye, so, too, should we be repulsed by sin. Christ is saying we must submit ourselves to radical surgery, so to speak, in order to save our souls. By God's grace, flee from sin, cut it off (and we discuss some ways to do so related to sexual sin) and learn to live contentedly with the one who is surely your better half.