For it goes so easily to join the dance of pleasure; but when it has gone apace, and it is pleasure which dances with the man against his will – that is a heavy dance! And it is so eay to give rein to the passions – audacious speed, one scarcely can follow it with the eye! – until passion, having taken the bit in its teeth, goes with a still more audacious speed – the man himself is not audacious enough to look where they are going! – carries him forcibly along with it! And it is so easy to permit a sinful thought! – it is so easy, it does not here apply as in other instances that it is the first step which costs, oh, no it costs nothing whatever, on the contrary, the sinful thought pays for itself at an exorbitant rate, it costs nothing – until at the conclusion, when thou must be pay for this first which did not cost anything; for when the sinful thought has gain entrance, it exacts a fearful price. Sin usually enters a man as a flatter; but then when the man has become a slave of sin – that is a frightful servitude, a narrow, prodigiously narrow way to perdition!
Soren Kierkegaard, For Self-Examination and Judge for Yourselves! And Three Discourses, trans. Walter Lowrie (Princeton: Princeton University Press, 1974), 86-87.