What is Harshing My Mellow?
1.
Bringing down my good mood.
I didn't like her.. she was really harshing my mellow, man.
See
2.
When someone takes away from your high, or tries to be cool by fucking with you when you are buzzed. What happens when a nancy (see Nancy) brings down your elated feelings while high.
Dude, you're really harshin' my mellow.
See