Ace feeling better today than he felt yesterday

Ace felt good enough to go to lunch and to the movies.  He took a Zofran yesterday and today which helped the nauseas feelings he had.  Can't figure out why some days he feels good and other days he feels bad.  He feels better when he drinks a lot of water I think.  He also slept in the bed most of the night instead of the chair.  Today was a good day.