the only way is one day wene you go into tom nooks shop and he will be sad talk to him and
he will say somthing diffrent

Yes, you can't get him to say anything else apart from the day he's sad.
And also somedays Blathers in the Museum is also sad, and sometimes he's sad for different
reasons. Talk to him! :)

heyo

But why are they sad? They don't really tell you and theres no way to help? To me its a
bit pointless.