Many ask, how can Hashem accomplish the destiny He created the world for through human beings who have free-will and can do as they please? Parshas Vayeshev is a good place to begin investigating this question.
There was once a place called Luz where people never said anything non-factual, and, as a result, no one ever died there. This does not mean that people there lived forever, but that when they were destined to die Hashem put a desire in their heart to go elsewhere, and there they died. Similarly, Hashem wanted the holy family of Yaakov Avinu to go down to the profane land of Egypt, the last place in the world they would have wanted to go. Gently, gently, like a merciful father, Hashem nudged them down slowly against their will (despite their free-choice) to the inevitable slavery they needed in Egypt. Read the Parsha carefully and you will see, scene after scene, act after act, how the drama unfolds.
The holy Zohar compares the development of the Jewish nation in Egypt to the development of an embryo in utero. Just as a wife receives an unnoticable seed and develops all of its limbs and organs and then bursts out in frightening contractions and gives birth to a child, so did Egypt nurture us into nationhood. Similarly, just as a wife would rarely get pregnant willingly if not for a tremendously strong attraction, so Yaakov's family had to be enticed to 'impregnate' the land of Egypt with their seed. Although the almost uncontrollable desire to cohabit does not make any sense, without it the human race would have become an extinct species many generations ago. It is a pull that must be controlled, but without it we would not exist.
Yes, people do have free will, they can swim, but in the long run the sway of the currents bring them to the shores best for them.
Adapted from Rabbi Vali's book on Bereshis. Questions and subscriptions can be mailed to: the Yeshiva