I believe it means that no one who acts good can stay good
Nothing gold can stay means that nothing that is new or beautiful can stay forever. The poem meant, when you are a kid your gold. New to the world, but as you get older, everything is getting old....
enjoying the simple things in life befor yu die
Robert Frost wrote "Nothing Gold Can Stay." He also wrote the poem "Stopping by Woods on a Snowy Evening."
It really depends on what you think but, in my opinion it is sad or melancholy.