i went on my first downswing in forever and lost almost $100, but I just got it back and more.
The way I see it, there are two things at work. The most important one being that when you are winning it is all attributed to skill and never good cards / flops / unlucky situations for your opponent.
But secondly, just by nature, certain times of certain periods work less than others. I always felt that some games were rubbish (such as a FL tourny and the $10 CC tourny today
and some games worked wayyy too well- sunday 100k (but i played poorly) and a $10 sng. but that between games everything worked itself out -- but then i lost over and over again so there obviously is variance that exists on multiple levels.
variance exists between running dry for a few orbits, an entire game, a series of games etc, with shorter time periods being more common than longer ones. in general though, if you play well and play against people who don't play well, you'll always come out ahead sooner or later..