The Kaf Hachaim writes (Hilchos Pesach 474:152) that all of the Divine lights that are revealed on the night when the Jews left Egypt are revealed again each year on Pesach. This is why everyone feels enlightened and joyous on Pesach, more than on all other days.
Sefer Zera Kodesh writes that the lofty levels of understanding that one can reach on the first night of Pesach go above and beyond even the levels of understanding Klal Yisroel attained at the Yam Suf.