I prefer to think about how your own skill reflects in a game, you cannot possibly play your best every single day, It depends on your frame of mind, or your relationship with a partner, even the weather outside can effect your game.
I prefer to play when there is a lot of wind and rain outside, as I don't feel as guilty playing Poker, as I do when the sunshine is beaming down. (I could be doing something better).
I suppose that is another reason Casino's don't have windows, so you don't realise what the weather is like, or what time it is.
Skill comes from study and practice, and it takes time to become skillful, like someone once said "Poker is a game you can learn in 10 minutes, But it takes a lifetime to master" there is no truer words spoken about Poker,
You can read all the books in the World on how to fly a Helicopter, but until you sit in the pilots seat and experience it first hand, you ain't going to fly. It is all about practice, practice, practice, and more practice,
It is that simple.
When the fun Stops, STOP!