The feeling you get when your significant other lays eyes on you, kisses you, or even just says your name, and you feel like you'd float away if it wasn't for gravity holding you back. Usually this is early on in the relationship, or possibly even before the relationship has started. This is the greatest feeling in the world.
No example for The Butterfly State. You need to have experienced it to know the feeling. It is the most satisfying feeling ever.