I would bring Ernst von Dohnanyi's Variations on a Nursery Theme: (it should start after the long and overblown introduction which I don't like LoL)
I don't think it should come as a surprise that I picked a variations piece - it has lots of variety that would keep me entertained for a long time! These variations are mostly light-hearted and fun which would always cheer me up and bring new potential musical ideas into my mind.