Vayomer Yaakov el Lavan hava es ishti ki mal'oo yomai v'avo'ah eileha - Yaakov said to Lavan, "Give me my wife, for my term is completed; and I will consummate the marriage with her" (Breishis 29:21)
Superficially the phrase "ki mal'oo yomai" would seem to mean my years of work to which I committed per the terms of our agreement are complete. Chazal, however, reveal a deeper meaning. Yaakov could have simply said "the time is up". The emphatic, personalized "ki mal'oo yomai" expresses a sense of urgency. "Ki mal'oo yomai" - my time has come. How can I fulfill my divinely ordained mission of fathering twelve tribes unless I marry now?
Upon reflection there is a remarkable message in Yaakov Avinu's words. On the one hand, he knows through ruach hakodesh that he is destined to father twelve tribes. Yet on the other and, he is very concerned that he may not do so. The message is clear: Hashem may prepare a destiny for us but He does not decree fulfillment of that destiny. We must, with alacrity and determination, apply ourselves to realize our destiny. Hashem may assign us a role in history, but we must carry out that assignment. Otherwise, our destiny will remain unfulfilled and Hashem will find other means to guide history according to His will.
Indeed Chazal tell us that Yosef Hatzaddik was also destined to father twelve tribes. Due to sin, however, he only fathered two and the remaining ten were fathered by Binyamin. The Netziv poignantly describes how his parents were ready to send him away from the beis medrash to learn a trade because they felt he was not applying himself. The Netziv, in tears, pleaded with his parents for another chance. They relented, and he became the gadol that he was who authored Ha'amek She'eilah, Merumei Sadeh, Ha'amek Davar, and other classics. As an old man the Netziv said, "had I not persevered, when I came to shomayim I would have been shown all of these seforim that I was destined to write. But then it would have been too late."
Personal destinies can remain unfulfilled. Like Yaakov Avinu we need to seize the day with its opportunities to fulfill our destiny.