After Yosef revealed himself to his brothers, they were instructed to travel to Cana'an and return to Mitzrayim with their father, Yaakov. Yaakov then packed his belongings and began the journey toward Mitzrayim. On the way down he stopped in Be'er Sheva, and brought sacrifices. It is there that Hashem came to him in a dream: "I am the G-d, the G-d of your father. Do not fear from descending to Mitzrayim, for I will make you into a great nation there. I will descend with you and I will bring you up" (Bereishis 46, 3-4).
Rav Wolbe (Shiurei Chumash) asks that Yaakov knew that a terrible exile of more than two hundred years awaited him and his offspring. If so, how did Hashem succeed in calming Yaakov by telling him not to fear, "for I will make you into a great nation there" and "I will descend with you and I will bring you up?" Why was he not to fear the many years of exile combined with backbreaking labor which were extremely foreboding?
A similar question can be asked in Parshas Vayishlach. The Torah tells us that on the way back to Cana'an, Rochel went in to labor and had difficulty in her childbirth. The midwife reassured her, "Have no fear for this one is also a son for you" (ibid. 35, 17). Here, too, the question begs to be asked. Not only was Rochel experiencing difficulty in her childbirth, she actually died as a result. If so, why was she expected to be calmed with the knowledge that the child was a boy?
The answer, says Rav Wolbe, is that the only true fear is a fear of not achieving the intended purpose of one's actions, trials or tribulations. Hashem was reassuring Yaakov that the backbreaking labor of the exile was all for a purpose of forging them into a chosen nation, and that purpose would ultimately be achieved. Likewise, the midwife reassured Rochel that even though she was having a difficult labor and might possibly die from the ordeal, she need not fear, for she had accomplished her mission and achieved the goal for which she yearned and strived. She had given birth to her second sheivet - the final sheivet of Yisrael.
We can't always know if our actions will achieve their intended purpose. Nevertheless, we must do our best and Hashem will produce the outcome as He sees fit. Yet, there are some actions that we need not fear lest they achieve their intended purpose. Torah, Avodah and Gemilus Chasadim are the purpose for our existence, and their performance always achieves the desired outcome.