1. I once went to a shiur on Yom tov, where someone asked “Why on yomtov do we eat sleep eat sleep eat sleep eat sleep?” The Rov, got very upset and said, “Don’t you daven!?” and then went into a half an hour mussar shmuess on the subject that Yomim tovim are only given for people to learn Torah. So advice number one is, Take a sefer, any sefer and sit and learn an hour or two.
2. Eat a milchik or parev meal on second night, or if you are makpid on meat, have cold cuts or something light.
3. Take walks or at least spend some time outside in the fresh air.
4. Cold showers are not fun, but it sure wakes you up for the next tfila. There is a mitzva called “Lo teshaktzu”, as well as the bein odom lechaveiro issues.