If the answer to "What did you gain over Yom Tov?" is "5 pounds," then there is something wrong, and not just with your weight.
Sefas Emes writes that "shalosh pe'amim ba'shana yeira'eh kol zechurcha es pnei Hashem" is not just a mitzvah -- it's a bracha. How incredible is it that 3 times a year the simplest Jew can come to Yerushalayim and experience seeing Hashem's presence!
It's true, we have no mikdash. Nonetheless, the Tiferes Shlomo derech derush writes that "makrivim af al pi she'ain bayis" means that the service in our hearts triggers the same avodah in beis hamikdash shel maalah that would have taken place here. "Se'irei izim naaseh b' ratzon" -- with our ratzon, our desire to do avodah, we can offer korbanos even if we are not yet capable b'poel of doing so.
After every chag (esp pesach - see gra in maaseh rav) there is an idea of neilas hachag. Neilah here is like "barzel u'nechoshes minalecha" -- it means a lock. As Yom Tov departs, we have to lock in our spiritual gains and not let them escape or evaporate.