The Rambam opens his Sefer HaMitzvot as well as his Mishna Torah with the mitzvah of believing in G-d: "anochi Hashem Elokecha" "I am the L-rd your G-d." Hashem said to Moshe Rabenu just before Matan Torah "that the people might hear that I speak with you and believe in you forever". A major purpose of Ma'amad Har Sinai was to entrench the belief in G-d in the hearts of the Jewish people for all generations.
Emunah is the first Mitzvah, and if you will, the sum total of all of the mitzvot, as we are taught in Massechet Makkot. The prophet Habakuk was able to encapsulate the message of all 613 mitzvot with the statement: "the righteous person shall live through his faith" (Habakuk 2:4).
The Torah records in Parshat Vayeshev how Potiphar's wife attempted to seduce Yoseph. We find two different approaches in the Gemara regarding how Yoseph managed to overcome his temptation to sin.
The Talmud in Yoma 35b describes Yoseph's response to the enticement and threats of the wife of Potiphar: When she said I will imprison you, Yoseph responded "Hashem releases the imprisoned". When she said I will blind your eyes, he responded "Hashem opens the eyes of the blind". And when she threatened to crush him, he responded "Hashem straightens those who are bent". Not the beautiful, powerful wife of Potiphar, nor any other power in the world could ultimately prevail over the will of G-d.

On the other hand, the Gemara in Massechet Sotah describes that what gave Yoseph the spiritual strength to overcome his temptation was that his father's image suddenly appeared to him. The Talmud adds that Yoseph saw his father warning him that if he sinned, he would be removed from Yaakov's family and would lose his status as a member of the Chosen People. The Gemara here is emphasizing that a sense of tradition and upbringing in his formative years allowed him to remain strong and stand up to these difficult challenges. The strong emunah which Yoseph lived and experienced in his early days burst forth like a flame and protected him from this potential crisis.
It seems that there were two forces which helped Yoseph overcome this situation.
The latter Gemara which we cited teaches us that the basis of a person's faith is established in his home. On the other hand, the Gemara in Yoma teaches us how Yoseph was able to apply the lesson he learned in his father's home and to build upon them. The message of emunah was deeply inculcated giving him the ability to apply it to challenges he would never have dreamed of as a youth.
These two gemarot teach us that his father's image, which represents his formative education, is not sufficient to protect a person, a person must develop that extra dimension of personal emunah which can then be applied to such a trying situation.
We open the daily Amida with "the G-d of Abraham, the G-d of Isaac, and the G-d of Jacob". Why not state simply 'the G-d of Abraham, Isaac, and Jacob'? Rav Ephraim Zalman Margolios (1762-1839) in Tshuvot Beis Ephraim answers that Isaac's belief was not just an inherited belief of Abraham's teachings, but was developed and internalized by Isaac himself. So too with Jacob, and so too, we may add, with Joseph. True, basic emunah he learned from his father as epitomized by the image of his father that appeared to him, but he was also able to cultivate and individualize his emunah and put it to the test when confronted with his own challenges and trials.
We too, must build on the faith which we were taught by our parents and our teachers. The more we develop, internalize, and personalize our emunah, the stronger it will be. As we have seen, deeply rooted emunah will get us through tough times and circumstances, times when we too are put to the test.