The "Ohr Sameach" (on the Torah, Parshat Bo, in the section beginning with "And in the Gemara") explains that the story of the Exodus from Egypt and the obligation to see oneself as if they personally left Egypt are one and the same. By envisioning this in one's mind, a person feels the obligation to give thanks for their own redemption. This is also related to the mitzvah of telling the story of the Exodus to one's children. He writes, "A blind person is exempt from the mitzvah of 'Vehigadeta' (and you shall tell), because they lack the capacity for emotional excitement. Since they do not enjoy the delights of creation, they do not care whether they are imprisoned or free. Therefore, they do not have the feeling of gratitude and praise for our redemption and the salvation of our souls, and consequently, they have nothing to tell their children." (End of quote).