In my opinion, a casual is someone who:
-focuses on having fun with the content, instead of burning through content as fast as possible
-tends to have more personalized goals regarding the game
-doesn't care about how long it takes them to achieve goals
- Has a more easy going attitude when it comes to the game
- Are less concerned on how they measure up to the next person(Again, have more personal goals)
- Are more likely to say "I am good/bad at this game," than "I am good/bad because I perform well/badly in the game."
I don't think length of time you play the game matters on whether you are casual or hardcore, because someone could be very casual in the way they play, and simply have a lot of time on their hands.
Anyway, I think a casual player is more likely to be happy at the end of a game because they don't think the game determines who they are, so they are able to take losses a bit better. They also are able to put down the game and walk away, instead of getting angry or sore over it.