The mishnah (Pesachim 116:b) mandates that in every generation a person is obligated to look at himself as though he personally departed from Egypt. The Rambam, (Hilchos Chametz U'matzah 7:6,7) cites this command as the reason for our reclining and drinking four cups of wine at the seder. The Alter of Slabodka is purported to have said that this is the most challenging mitzvah of the night of Pesach.
At first glance, the mishnah is teaching that the level of hakoras hatov we must all have at the seder is not simply for what He did for our ancestors and that we would not be where we are today were it not for His kindnesses afforded them, rather, we must look at the exodus and express a personal hakoras hatov for what He did for us.
The birkas ha-gomel, thanksgiving blessing, is mandated by the Talmud (Berachos 54b) for the following four survivors: (a) one who completed a sea journey (b) one who completed a hazardous land journey such as crossing a dessert, (c) one who recovered from a serious illness (d) one released from captivity. Interestingly, our meal at the seder is upgraded to a seudas ho'da'ah - meal of thanksgiving, as upon leaving Egypt we successfully experienced all four. The Alshich asks, if the motivation and cause for the thanksgiving is appreciation for what Hashem has done, than in reality we should be reciting this blessing constantly, as his kindnesses are with us always. Therefore, he teaches it is not only the salvation from these threatening circumstances, but as the verse in Tehillim (107:24) which is the scriptural source for this blessing states "they have seen the deeds of Hashem". When one hears of the salvation that another experienced, it bolsters their faith in G-D, and His personal involvement in the affairs of man. When however, an individual experiences a personal life-saving situation, they are giving thanks for the privilege of seeing G-D first hand. A miraculous outcome for someone else solidifies my belief intellectually, but when I am the direct recipient of His kindness my Emunah-faith is elevated to a tangible experiential level.
Tehillim (33:1) states: "ranenu tzadikim Ba'Shem - sing joyfully oh righteous because of Hashem." The Medrash Shocher Tov points out that it does not say "el Hashem" which would mean sing to Hashem, rather Ba'Shem, understood that as soon as they are privileged to see the Devine they sing. Thus, we find immediately prior to the miraculous rescue at Yam Suf, (Shemos 14:31) "Israel saw the great hand that Hashem inflicted upon Egypt", and immediately thereafter, (15:1) "then Moshe and the children of Israel sang this song". We also find at the opening day ceremony to the inauguration of the Mishkan that the Torah teaches (Vayikra 9:24), "A fire went forth from before Hashem, the people saw, and sang glad song". Similarly, the prophet Micha (7:15) promises "as in the days when you left the land of Egypt, I will show it (Jewish people) wonders". And lastly, we also pray in the daily in every shemoneh esrei, "may our eyes witness Your return to Zion".
The Talmud (Berachos 12a) explains why the Shema in the morning is followed by the blessing of Emes veyatziv, while that of the night is followed by Emes v'emunah, by citing the passuk (Tehillim 92:3) "to relate your kindness in the morning and your faith at night." Why do we focus on "kindness" in the morning but on "faith" at night? Daytime represents clarity, when one can see and comprehend with certainty; things are "clear as day", as the saying goes. This refers to the kindnesses and miracles that He performed for us. Nighttime, however, indicates the doubt and uncertainty we may have as to when and how we will be extricated from our communal and personal challenges. As such, nighttime is a time to draw upon one's faith that redemption- geulah will come.
The majority of mitzvos - shofar, lulav, tefillin, hallel - are all day mitzvos, reflecting the positive and open relationship between Hashem and Israel. Why, asks the Vilna Gaon in his Oros HaGrah, are the mitzvos of Pesach - eating the korban Pesach, matzoh, and marror - all night mitzvos? His answer is that the night of Pesach is philosophically and halachically a day. Similarly the Gaon explains that although the Torah says (Shemos 13:8), "you shall tell your son on that day" when describing the mitzvah of sippur yetzias mitzraim, we fulfill this mitzvah at night since this night is axiologically a day. We experienced on this night His presence with such clarity that the character of this night was forever transformed from a night of faith to a virtual daytime of seeing.
Thus, the charge to "look at oneself as if they personally left Egypt" means not only to attempt to put oneself back in time over three thousand years ago, but rather to know with absolute surety that Hashem, the Honored Guest at our seder, will solve our communal and personal pressing problems.