We cannot always influence reality, but we can always influence its interpretation. When Yosef and his brothers meet, reality is harsh and bitter. After all, the brothers sold him and abandoned him to his fate. And still, Yosef manages to unite the family by giving positive interpretation to the dry facts through looking at reality with an optimistic look, one which is full of faith. Pay attention to the amazing words he says to the brothers, when he reveals to them that he is Yosef:
"וְעַתָּה אַל תֵּעָצְבוּ וְאַל יִחַר בְּעֵינֵיכֶם כִּי מְכַרְתֶּם אֹתִי הֵנָּה, כִּי לְמִחְיָה שְׁלָחַנִי אֱלֹוקים לִפְנֵיכֶם... וְעַתָּה, לֹא אַתֶּם שְׁלַחְתֶּם אֹתִי הֵנָּה כִּי הָאֱלֹוקים."("And now be not grieved, nor angry with yourselves, that you sold me hither; for G-d did send me before you to preserve life... it was not you that sent me hither, but G-d.")
Yosef explains to them how he was actually SENT to Egypt to rise to power there, so that he could save the family and the entire region in the time of famine. The brothers cannot undo what they did, Yosef cannot erase the tragedy he went through - but he can decide how to look at it. Should he complain, seek revenge, hold a grudge? Or should he find the blessing within the curse? He chooses an outlook that can benefit us too, in any situation in which we may find ourselves: "for G-d did send me before you to preserve life". If I was sent here, I must think how I can derive benefit from this - for myself and for others.