Indeed, show-offs have a stinky attitude.
1 mistake we shouldn't make though is judge a person based on their response to the music they are playing or singing, unless if it's pretty clear that they are showing off.
I am a nervous person & sometimes I shake whilst playing when the music is not on, but once it's playtime, I seem to move with the song, but I don't stick my tongue out to the girls in the front row, play out louder than everyone, wink at people or do anything I'm aware of that it's an element of show-off.
I think show-offs know themselves best & that easily manifests itself in quite a short space of time.
I agree with everyone- show-off have a low self-esteem & that is revealed more nakedly when someone better comes & they feel like sinking their head in the sand
