-You know you're a guitarist when you hang guitars on your walls instead of a portraits as decorations.
-You know you're a guitarist when feel you're 30 kilos lighter after reaching home from a jamming session.
-You know you're a guitarist when you try to make your guitar sound like every other instrument (except a guitar).
-You know you're a guitarist when the word 'tone' means everything to you even when you don't know what exactly it is.
-You know you're a guitarist when you're poor, your wife left you and you fight for the custody of your guitars instead of your kids XD