For me it's absolute best when I get in to the 'creative zone' - working without any patterns, just creating whatever comes to mind and making it up as I go along.
In my perfect experience I would have inspiration after inspiration, and everything would turn out even better than I had just imagined it, and my neck would never cramp up, my fingers would never get sore, my needles would thread themselves and my hand-sewing thread would definitely never tangle! Throw in a nice rainy day and a cozy dog sleeping at my feet as the icing on the cake and I could stay there forever!