old wine, clean clothes and meat
and happy memories of what happened in the past, even the recent past.
this is happiness. this is simcha
(discussion about the command to be happy on a festive day, simcha, if that applies on the first night. there is an opinion that it doesn't as the first night is the start of the festival, with no festive day preceeding it. Other ways to be happy include having: clean clothes, old wine, and the sacrificial meat.)